Nobody needs the railroad’s permission. We just build the rails in the same way we built the freeways, which by the way, are going to hell in a handbasket because we won’t pay to maintain them.
It’s obvious the airlines can’t handle the transportation needs of the country. Let’s take some of the load off their backs. And de-regulation appears to be a failure.
There’s another problem, a simple one which I can’t believe I forgot to metion earlier - noise. However comfortable modern high-speed trains are inside, they’re really fucking noisy when they go past (after all, it’s nearly the speed that Concorde took off at). Most such railways have big sound barriers, earth banks and so on, when there’s the likelihood of the noise causing problems. And I certainly would see it causing problems if directly above a road, both from distracting drivers and also by it becoming a target of much hostility.
Running a high-speed line over the median of a freeway would have the same problems as the Acela corridor; the turns and hills were designed for cars going 70 mph, and are probably too extreme (in some places) for a train going 180.
I took a German ICE from Brussels to Frankfurt about a month ago. For some of its length, they have the tracks running next to the autobahn, maybe 50 to 100 meters away and with curves and grades within spec. It didn’t seem to have any trouble climbing the hills, but it looked like some of the hill crests would be too sharp (think of a rollercoaster) so there were dozens of short tunnels where the train cut through the top of a hill. There are still issues with buying the land, and all those tunnels can’t be cheap, but I think that would be a good plan to examine and see if it could work in the U.S.
(And I have to say, looking over the engineer’s shoulder, lights flashing past at 296 km/h is one hell of a good ride.)