Flying has been the preferred travel mode of both the well-to-do and the aspirational for over half a century. Air travel only needs working airplanes, and a relatively simple airport at each end. So, in general, there's ample social pressure to get the job done quickly.

Vs. high-speed trains went out of fashion (in America) well before most people's memories. And their tracks have to be threaded, foot-by-foot, across a landscape which is overflowing with red tape and jurisdictions and NIMBY's and existing infrastructure. Said threading to be planned by yet more politicians and bureaucrats and planners, then done by America's low-functioning construction industry.

Nations with good high-speed rail systems have quite different priorities and local governance structures than America.