A lot would depend on the circumstances, such as does the French empire survive, does Prussia/N Germany see the OTL dramatic economic growth and the like. A hell of a lot can change and it should be remembered it was only in 1904 that Britain signed the entente with France [and 1907 with Russia] because of the growing threat and hostility from Berlin. Before that France and Russia were still seen as the primary threats. Also another factor for this was the Russo-Japanese war as with both allied to France and Britain respectively and especially after the Dogger Bank incident both Paris and London found themselves pulled into an unwanted war to support their allies.
In terms of Italy I would suspect that the French presence in Rome wouldn't last and that Italy would achieve a large scale level of unification. As such its likely to be another member of the Anglo-German alliance if such a balance of powers occurs, along with probably a modernising Japan for geographic reasons. Italy did perform badly but this was partly due to one of the worst C-in-C's in the war [which is saying something]
Luigi Cadorna - Wikipedia and also due to a very poor position for offensive actions. Italy on the defensive might perform markedly better, at least in terms of holding off hostile forces and inflicting heavy losses.
One other issue is that it could be difficult to see both Austria/S Germany and Russia in the same alliance as both have opposing designs in the Balkan region. That's why Germany ultimately decided it had to choose between the two and - in part guided by national/racial issues especially possibly by the Kaiser - picked Austria, which is seen as the worst case by many. The relatively moderate terms imposed on Austria after 1866 meant that its relations with Prussia/Germany were fairly good and in this scenario if Russia is aligned with France your likely to see Austria [+S Germany but call it that for simplicity] aligned with Germany. In which case it would probably be Britain-N Germany-Austria v France-Russia-Italy, although with the latter's reliance on coastal trade and imports Italy could decide to sit it out or see who offers the best bribes for the risk.
One other issue if France won big of course, although it sounds like you don't want to go there. It could end up crippling Prussia if say it restored Hanoverian independence, split off the Rhineland/Westphalia region as a separate state and/or cosied up to Austria by insisting on the latter getting Silesia from Prussia. A couple of those would seriously weaken Berlin as a rival to either Paris or Vienna and all three could end its position as a great power.
Anyway initial wild thoughts on what might be possibilities.
Steve
Yeah, honestly I can see Russia going with either the Austro-French or the Anglo-Germans here. With the former they can snatch at Prussian Poland, East Prussia and whatever they want from the Turks, in addition to trying to win their Great Game against Britain; the latter can promise them Austrian Galicia, the reassertion of their leadership over the Slavs as a whole, and almost total mastery over the Balkans (constrained only by the Turks and their British backers). I'd imagine what Russia ends up doing will come down to who the Tsars hate more, the British or the Austrians. Even if a Franco-Austro-Russian 'Entente' does form and defeat its enemies, I think it'd be easy for Russia to fall out with its former allies over the Balkans, Middle East (France did fight Russia in the Crimean War because of its own pretensions to becoming the 'Defender of Middle Eastern Christians' after all) and possibly Poland (the Bonapartes were big fans of the Poles, though since this would be a point of friction with Austria too, I don't think France would push too hard on this point).
Italy I could see only taking Rome and ending the Papal States if France pulls out its garrison at a later point in time. But tbh I don't see them doing so unless there's another emergency that would require such an evacuation of the Roman garrison, such as alt-WW1 starting anyway. To my understanding Napoleon III only kept the garrison in place because of the influence of his wife, Empress Eugenie de Montijo, who was a devout ultramontane Catholic; and Eugenie had a strong influence on their son Napoleon IV, who was similarly religious. As Napoleon IV wouldn't be in any position to join the British Army and get himself killed fighting Zulus in a '2nd Empire survives' timeline, I think he'd agree with his mother and keep the French in Rome for as long as possible, although that in itself could be an alternate spark for the ITL WW1 if the Italians ever get a government that's tired of waiting and decides to try seizing Rome while the French are still there (presumably they'd only risk it with British/Prussian support). Italy did seem to do better on the defensive, but that was while they only had one front to deal with, and the French were actively helping them rather than being at war with them IRL - if Cadorna is still in command, I shudder to think of all those Italian troops he's going to get killed as he tries to deal with both France
and Austria.
Speaking of Nappy IV, I think it'd be fun to speculate what goes on with the politics of European royal marriages while he lives and becomes Emperor of France. Apparently he courted the British princess Beatrice, Queen Victoria's youngest daughter, but died before they could marry IOTL; such a marriage may well not pan out (and Napoleon might not even get to meet her at all) if France and Britain are hostile to each other, but if it did, it could either be a point toward Anglo-French reconciliation or (much like WW1's personal effects on European royalty) fail to prevent war and result in Napoleon fighting his nephew George V. There was also suggestion of a match to the Infanta Maria del Pilar, a daughter of the Spanish queen Isabella II, who historically died right after Napoleon IV himself did. Finally if France is looking to align with Austria, Napoleon could seek the hand of Franz Josef's eldest surviving daughter Gisela - she's the same age as him and it wouldn't be the first time a Bonaparte married a Habsburg princess.
Yes, I'm pretty doubtful of France winning such a stunning victory over Prussia in 1870 - just getting them to not lose the war and make small gains is tough enough, considering all the disadvantages they had going in. Instead such a partition sounds like the sort of thing France might demand of Prussia if they completely crush the latter in an alt-WW1, with the aim of permanently castrating its German rival and asserting itself as the uncontested continental hegemon.
While it would likely result in Bismarck getting sacked and the status quo of the 1850s, it probably only delays the rise of Germany rather than prevents it. German nationalism as a whole was on a serious rise, and anything that seeks to check it probably results in the Germans taking a swipe at the French down the line, though this war would be with British support since Britain has every reason to side with Prussia & Co.
Italy either won’t do jack or side with the Catholics because they’re caught between Austria (which, even when allied with them was still making war plans to invade Italy), Britain and the RN would absolutely crush their navy, and France (less of a threat, but still a threat).
I agree, Britain would feel threatened by a stronger & bolder France (which in turn is going to be less willing to accommodate British colonial demands) and seek out Prussia/the NGF as a counterweight to Bonapartist power on the continent. Even if France does manage to crush Prussia on the continent (if they can get Austria and even better, Russia on their side) I have a pretty hard time seeing them being able to land any army in Britain itself, thanks to the Royal Navy. They'd probably have to content themselves with nipping at Britain's colonies instead, particularly (if not entirely) in Africa.
Aside from the Anglo-French colonial rivalry and Prussian revanchism & desire to finally unite Germany, I think Italian nationalism and the desire to complete the Risorgimento is the next most likely trigger for the alt-WW1, unless France has returned Rome in which case (as you say) I don't think they'll have any strong enough reason to pick a fight with the French (they could seek French Savoy and the Austrian Littoral & Trentino, but these don't seem nearly as big a prize as Rome itself). Even then they surely wouldn't move without Anglo-Prussian assurances, since simultaneously fighting France and Austria with support from the greater powers will be hard enough; doing so alone would be obviously suicidal to even the most overconfident Italian nationalist.
Papal States survive, Italian 'unification' thwarted. Holy Alliance restored, now with France, Bavaria, Serbia, Papal State, and Kingdom of the Two Sicilies as members in addition to Austria-Hungary and The Russias. Prussia dismantled between an expanded Bavaria and restored Poland-Lithuania. Serbia joins A-H as the third Crown in the now Triple Monarchy. HRE restored as an alternative to German unification.
Britain is kept out of the continent except for minor allies/dependencies in Lombardy, Sardina, Spain, and Portugal. The next war is in the East as Britain-Japan-America fight Russia and her allies for control of China and Tibet.
The only ways that France wins are 1) she doesn’t go to war with Prussia at all or 2) she fires all of her generals and replaces them with competent or better replacements. Problem there is, France is obsessed with a centralized chain of command and in routing all of its logistics through Paris, so that’s a very tall order (given that it nearly cost them the war in 1914 and did cost them the war in 1940).
At best, France annexes the Saarland and sets the stage for a different World War I (basically a repeat of the Napoleonic Wars). Russia has a huge population, but in 1870 they’re still a fair bit behind the 8-ball in terms of being able to field their army and keep it supplied. Not to mention that, as we saw in World War I, they largely suck at wars of maneuver and have incompetent commanders.
Most likely result of all this is that World War I is a giant replay of the Napoleonic Wars. What happens after is Germany winds up unifying in a different fashion, but likely still under Berlin’s aegis.
They consisted of basically just the city of Rome at this point, so at best only last until the next time France gets distracted.
Was already all but complete at this point and had been for a decade.
Why would this happen after Prussia loses its war? The Holy Alliance had been defunct since 1825 and its last vestiges had ended in 1853.
Even WW1 and WW2 didn't end with the losers being completely erased from the map and neither did the OTL Franco-Prussian War, why would this? The 19th century was an age largely of short, limited wars for small, limited goals.
This is where it really starts getting hilarious. Yes, just hand over the entirety of the Rhineland to Bavaria, lol.
Lolno, Russia and Austria are never gonna let this happen even if Prussia gets annihilated.
What does this have to do with anything? The Serbs historically were endlessly hostile to the Hapsburg crown and neither did the Austrians particularly want them. It took the assassination of the heir to the throne to get Austria to try and deal with Serbia OTL.
Again, why? Austria might well become suzerain of the German states if Prussia fails to defeat France; but the HRE had ceased to be for 70 years and prior to that existed in name only for two centuries before Napoleon put it out of its misery. Nobody was remotely interested in reviving it, as shown by the fact that no-one tried.
Look, this is pretty much just a wish list of "what I want to have happened in the 19th century" and not anything remotely plausible from the POD.
Yeah...I think that's a bit much, even for the most optimistic scenario for a French victory, whether in the FPW or an alt-WW1. France mostly just desired the Left Bank of the Rhine I think (the 'natural borders'), not to completely wipe Prussia off the face of the planet - I could see them partitioning the North German Confederation, in particular Hanover (to try to regain British goodwill, though I think that'd be misguided since the British never seemed to particularly want it in the 19th century even while still under Hanoverian kings) and Westphalia (to buttress their own border) as Stevep suggested.
Empowering Bavaria or Austria to such an extreme would also run contrary to France's own aim to be the unchallenged continental hegemon. And as Navarro said, I don't think Russia or Austria would approve of liberating Poland when that'd require both of them to give up quite a bit of their own territory, either. The only really plausible thing they might try out of that list, IMO, is totally dismantling Italy, and even that might be too difficult for Nappy IV to try - it would basically require the French & Austrians to occupy every inch of Italian soil first, and that would require a huge number of soldiers and resources be redirected away from fighting Prussia and Britain, almost certainly more than they could afford.
Instead, after some thought a Catholic imperial hegemony over Western and Central Europe directed from Paris, with Austria as a junior partner and Prussia decisively crippled while Russia dominates everything east of the Elbe and the British (as you say) locked out of the continent, seems to me like the most realistic outcome of a maximum French victory over all its enemies. A defeated Italy would be looking at having to cede Lazio back to the Pope (if they occupied it), the rest of Savoy to France and Venice & maybe Lombardy back to Austria; I'd expect the House of Savoy to get overthrown in favor of a republican and ultranationalist regime led by someone like Gabriele d'Annunzio or Julius Evola if such a scenario occurs, but they'd have a hard time finding allies to help them realize their revanchist fantasy if France continues to dominate Europe (maybe Britain after a couple years or decades of rebuilding & rearming?).
In that case, to paraphrase Hastings Ismay an utterly triumphant 'Entente' would be looking to keep the Austrians in, the British & Russians out, and the Germans & Italians down across the continent. But odds are none of this would come to pass unless France & friends win an extremely quick and smashing victory in an alt-WW1, which is much easier said than done (as everyone who thought they could win WW1 before Christmas IOTL found out).