Speaking or tech uplifts, have there ever been fics wherein the nobility actively resist it or hamper building those places on THEIR lands?
One of two things are true:
1) It's the Targaryens doing it when backed by dragons. In this case resistance is the height of idiocy and will result in some Fire and Blood and the throne shows why giant, army killing, castle melting, fire breathing lizards that can fly are the ultimate argument of Kings.
2) It's someone else pushing for the uplift. In this case it will never get done on any kind of continental scale as there are simply too many noble asses that need kissing and too many factions that would make it effectively impossible. Individual projects in individual kingdoms (or maybe two, if the right Lords Paramount are cooperating)? Sure. But anything beyond that? Highly unlikely.
I mean the biggest impact project would be the Northern Canal. And you could probably get the Lannisters and Arryn's onboard with helping fund and build that simply because of what it would do for their trade. If the Ironborn have an idiot on the throne, he might even let it happen as well on the theory that it will mean increased shipping to pirate in future (in reality, that would just get the Iron Islands genocided properly and turned into someone else's territory). The thing is, the Iron Throne without Dragons (or Robert's supreme idiocy) is NEVER going to allow that project to occur. Build that canal and you drastically undercut the Thrones ability to regulate trade with Braavos and the free cities more broadly. The Reach would also oppose as it frees Westerlands -> Braavos trade from having to go South, Dorne the same and for the same reasons.
The only times you could get such a project done are when the Dragons rule (because the Iron Throne has nothing to fear from the Northern Canal or the various Lords when it still has dragons) or when Robert is sitting the throne.
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For other projects, connecting the Trident to the Gods Eye (and making the relevant rivers navigable for barge traffic) and Blackwater Rush to Mandar would both be massive improvements but the only way that either would get done is with the Throne pushing for them.
Granted, again, the only time it could realistically be done is when the dragons were still around. Assuming the Targaryens were willing to use them as beasts of burden. I mean imagine the Black Dread digging ditches; in a matter of hours he could probably outperform a
modern construction company working for a week, much less what could be done with Westeros tech. Dragon power to dig out the canal, frame it lightly in wood, have the peons fill the wood frame with gravel/crushed rock, and then have the dragon fly down the canal to be with some nice flame; dragon fire can melt stone, so fusing the loose rock into something akin to cement should be no real problem.
You could do it without dragons, it would just take a lot longer and be a lot more expensive. The other thing is; who does it benefit?
Allow a barge to go from King's Landing to the Mandar and you are also allowing the Reach to use the same route for their supply train for an army marching on the Crownlands. Connect the Trident to the God's Eye and you do the same for the North, Riverlands, and Vale.
If the North puts a blocking force on the Twins and Bloody Gate they can pin the Vale and Riverlands in place while having a straight shot across the Ruby Ford to ravage the Crownlands; give them a canal to take from the Ford down and they can easily siege King's Landing from both sides. You also have to fear them being allowed to run rampant in the Reach, bypassing the crownlands entirely.
The Vale could do much the same thing; rush a blocking force to hold the Ford, load the army on to be barged south to King's Landing while a second threatens the Crownlands proper.
For a throne without dragons to be safe while improving transport infrastructure, the throne also needs a very large royal army. And the nobility is never going to allow a King without dragons to build a proper royal army of the needed size, even assuming that the King could fund it. A king with a hundred thousand professional soldiers under arms needs to find enemies to justify the expense and is able to force his nobles to bow. The throne will quickly find excuses to essentially absorb the whole of the Riverlands into the Crownlands; because build castles to hold the Golden Tooth, Deep Den, Twins, and Rubyford and those natural chokepoints give the throne an almost unassailable base. Except then the triangle made by the Blackwater and forks of the Mandar then becomes a really juicy prize to grab off at the first opportunity.
The Lords Paramount can read maps, and none of them want a more powerful Throne. They won't allow a royal army of real size to be created simple because of what it will inevitable be used for (grabbing off
their lands for the Throne). Nor will the lesser nobles be inclined to support it given that a royal army undercuts the power of the knightly houses and Knights.
The dragon backed Targaryens could have done it (and should have probably), but that would have meant generations before a Targaryen could even pretend to sit an easy throne.
