Infrastructure change at the scale you're speaking about is not unheard of. The Netherlands did it twice. First because Europe got the shit bombed out of it and building car centric cities was trendy, then second because they realized what a shit idea that was and reversed it.

Sure, the Netherlands was never sparse in the first place, but nobody's asking for trains to farmer John's house in Nebraska. If the Netherlands can rework their cities to at least chillax on cars, so can American cities.

I know using the Netherlands as an example is trite, but urban planners literally know the solutions.