I think that a lot of European nations, and a lot of people in the USA, watched the US play whack-a-mole in the sandbox for two decades, and thought that was what 'real war' was like logistically and economically.
The war in Ukraine has woken people up to the fact that full-scale war is a lot more demanding.
Anyone who thought Iraq/Afghanistan was a real war in any way was/is a fucking idiot.
Those were occupations/nation building done under incredibly restrictive rules of engagement and with minimal to no non-military investment.
Ukraine likewise isn't a "real war" in many respects. Ukraine's entire logistics base is outside of Ukraine proper and is effectively impossible for the Russians to engage (ignoring the military issues with striking at the logistics chain, doing so would have unacceptable political costs to Russia) and no one is really willing to go after Russian logistics outside of Ukraine proper. For gods sake the Ukrainians aren't even sinking Russian oil tankers (and they have that capability).
Ukraine is also the beneficiary of a lot of active US support when it comes to intelligence, communications, scouting, etc. To the level of the US providing precision targeting information to Ukrainian artillery for counter battery fire.
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If the US decided to go fight a proper war (without going nuclear) it would start with power plants, transformers, oil/gas depots, water treatment facilities, and critical transportation nodes all going away on zero notice in the middle of the night when a thousand cruise missiles fired from SSGN's start things off in coordination with B-2's and F-35's. In literally the opening ten minutes of the fight there would be no intact, operational, air defense facility in the target nation, no surviving naval vessels, no surviving air craft, and essentially no surviving tanks that weren't already dispersed. Communications would likewise be down across the nation, every internet connected device in the nation would be bricked, the power would be out, municipal water would be out, etc.
The US in a real war with basically unrestricted RoE (which is what you get in a real war) can basically destroy any other nations ability to make war or sustain its forces with virtually zero notice and from facilities thousands of miles away.
Taking the enemies territory would be a different question, but rendering harmless the enemy nation would basically redefine the very concept of what the world thinks a war is.
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And the US lead is only increasing as time passes. The next generation of US military satellites is going to be a militarized Starlink with ten thousand plus individual platforms providing 24/7 complete global communications, EWAR, ELINT, and surveillance capabilities along with sufficient broadband support to allow every single US platform from the infantry man on up to be networked in real time and with all of the data from all of those feeds being piped back into some of the worlds most capable supercomputers running all manner of AI and data mining algorithms to analyze all of that take, identify problems/opportunities, generate action plans, and feed those plans to the decision makers in essentially real time.
Then comes the US actually operationalizing Starwars. SpaceX has made the launch costs reasonable and allows a network of sufficient scale to actually intercept even a full strategic launch from every other power combined. The laser technology (along with the needed computer support) is already there. Seriously, within 20 years the US is going to have an actual, effective, missile defense system that will be able to detect, track, engage, and destroy ANYTHING that attempts to exit the atmosphere (including all ICBM's and SLMB's) at essentially limitless scale.
Note that the surveillance constellation will also allow what is essentially global AWACS coverage 24/7 with the US able to track in real time literally everything airborne or on the oceans surface above the size of a helicopter.
Then comes prompt global strike. One of the best defenses against laser based air defense systems is the plasma sheath that can be created by going fast enough through the atmosphere. One of the most cost effective ways to create that sheath is re-entry. The US will park a few tens of thousands of strike platforms in orbit and be able to drop any or even all of them on targets within less than an hour of the decision being made and with basically zero tells before they start de-orbiting. And with payloads running the gamut from spreading anti-personnel bomblets over a city block all the way up to wiping out a city.
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Note that the militarized Starlink analog along with improvements in AI, self driving, and automation will make the Abrams replacement a drone tank. Drone tanks that the US will be able to produce in essentially full automated factories by the hundreds of thousands if the US is so inclined. The same technology will be applied to artillery, transport, etc. The US will turn most combat into something that doesn't require sending anywhere near as many people into harms way.
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Russia - Ukraine is what you can expect when non-US parties make war on each other. But it will teach all the wrong lessons for any nation that wants to contest or even pretend to stand equal to the US.
The US has had the worlds most advanced, and largest, technological and industrial base for a century along with investing, on an annual basis, more on its national security establishment then the entire rest of the world combined spends in a decade every single year. This has been the case for, literally, fifty or so years. Note that during those fifty years the US has also had far and away the most active combat experience and is the world leader when it comes to learning from its combat experience.
This isn't the US being the varsity team while everyone else is the JV team. This is the US being the Super Bowl champs and everyone else playing in a children's summer league. The best of the rest might be rated at high school level, being generous.