People forget, the common denominator for countries that have high-speed rail networks, like the Japanese Bullet Train, the French TGV and the German ICE?
Every one of those countries had their rail infrastructure bombed into the stone age in WW2 and had the luxury of being able to rebuild it from the ground-up in a coordinated state-run effort by nationalizing the patchwork of private companies that had existed beforehand.
That never happened here.
In the US, the railroads are still running on legacy right-of-ways that date to the 19th Century in some places and were never designed for high-speed. The curves and grades are too extreme for safe travel above freeway speeds, the hard limit on most track is 70 - 80, and even that's not really possible in places where I live, like the Appalachians, too many mountains, too many curves, you'll be lucky to hit 40 most days. Also, the railroads in the US, in opposition to most of the world, are not nationalized, they're private companies and they are dedicated to freight hauling, they lease the lines for the national passenger service (Amtrak) but, again, due to the legacy nature of the track, they stopped being cutting-edge for passengers around the 1950's. US railroads accordingly dropped their passenger services in the late 60's and early 70's as unprofitable, and never looked back. So all those new suburbus and bedroom communities that grew around urban centers in the 50's? THey did so without a train station in them, trains were seen as a bygone lowtech thing, a car was liberating, you could go anywhere anytime, unbeholden to tickets, transfers and the whim of a timetable.
To change that? The cost, economic and political to just say "imminent domain!" and nationalize the railroads AND bulldoze the thousands of people in the way of straightening out tens of thousands of miles of track? It cannot be done.
So whenever someone wants to know why we don't have a high speed passenger rail system, it's because we have reached the limit of what we can develop without starting over from scratch, because nobody bombed us to smithereens 70 years ago.
Our car craziness isn't just because we won't take a train, circumstances has made it so that we largely cannot.