(For one example, check out the incomplete stub at the eastern terminus of I-70 -- I don't believe the cost of the land was a major factor in that case)
The reason we don't have nice things like China does is just political will, not any legal barriers.
States have their own eminent domain powers which vary, however in general they're easy to sandbag in the courts for years, preventing the state from doing anything while the landowners argue over the money.
[1] https://en.wikipedia.org/wiki/Federal_Declaration_of_Taking_...
Importantly those highways don't need to be free to use. The government can take land and build a for-profit railway, in conjunction with a private corporation if they want, as long as it was to benefit the public.
A major problem I have with this is appraisal prices often don't jive with reality. For example in San Fransisco houses almost always sell above asking, if the government were to step in and give the land away to a private person at asking they would be in effect getting a discount. Similarly my own home has had a lot of work put into it that doesn't effect it's appraisal price meaningfully, if forced to sell at that price I'd lose money.
https://www.bloomberg.com/news/articles/2021-07-02/supreme-c...
https://slatestarcodex.com/2017/02/09/considerations-on-cost...
At this point, they don't even pretend to respect the intelligence of the people.
A common-sense change might be requiring minimum quantities of local signatures to limit the potential impact of a small opposition.
https://en.wikipedia.org/wiki/California_Environmental_Quali...
"In one case, anti-abortion activists filed a CEQA lawsuit to try to block a new tenant (Planned Parenthood) from using an already constructed office building in South San Francisco. They cited the noise caused by their own protests as the environmental impact requiring mitigation. This lawsuit delayed the new tenancy by at least 18 months."
"Governor Jerry Brown, in an interview with UCLA's Blueprint magazine, commented on the use of CEQA for other than environmental reasons: "But it’s easier to build in Texas. It is. And maybe we could change that. But you know what? The trouble is the political climate, that's just kind of where we are. Very hard to — you can’t change CEQA [the California Environmental Quality Act]. BP: Why not? JB: The unions won’t let you because they use it as a hammer to get project labor agreements." "
In the PRC, if the government wants to build a high speed rail line, it's getting built and F-U if you want to stop it. In the US the process is 'democratized' and every little busybody comes out to protest the construction, drag the process out, or get some variance approved for some hitherto unexpected concern.