The US has enough empty/low-density land in it that every metropolis west of the Appalachians could be shadowed by completely new cities, with other approaches to planning and density beyond just building around the ubiquitous automobiles. Then people and businesses can just gradually move in.
This is something that China has apparently been doing for a long time, albeit with insufficient attention to quality control. They occasionally get buildings that have high-tension power lines running through the stairwells, or buildings that just suddenly fall over, and then the West points and laughs. But at least they are making gestures towards urbanizing their rural populace, and re-urbanizing their existing urbanites. As useful as planning is, at some point you have to actually start building, or you never get anything done.
But then again, looking at the sort of development effort invested in Olympic Villages, where a huge, concerted effort puts up a lot of new construction in a short amount of time, putting up whole cities at once can also turn into an embarrassing disaster rather quickly.
In the US, it just seems like city governments are holding the city infrastructure as hostage to squeeze some more ransom money out of the residents, then shooting the hostage anyway. It's very frustrating to watch in other cities, and absolutely infuriating in your own. How much would it cost, really, to abandon an old, sprawly city, and build something that starts with a bunch of solutions to well-known urban problems that can't even be implemented when there's already a city in the way?