American cities are clustered as much as European and there's hardly a good reason why high speed rail is impossible. To the point that there literally is a private company that built a high speed link between Orlando and Miami.

As for the experience of driving to a train station, that's compounded x times by going to an airport.

But in the end the lack of use stems more from discomfort, than anything else. Having high speed connection from Poughkeepsie/Albany to NYC would open up Hudson Valley to commuters decades ago, not a boom of Zoomtowns today (Kingston, NY, Beacon, NY)

The overall infrastructure is crap in US and that is the primary reason for poor use of it. (I mean, FFS, old Tappan Zee Bridge didn't even have pedestrian walkway! While being the only available crossing for miles)