I wish we could build these lines here. It was tried in the 1970s with a "high-speed" turbine-powered train. The train technology worked fine, but the train companies got permission to use cargo trains on the "high-speed" tracks. A loaded cargo car, of course, can weigh over five times what a passenger train does; it wasn't long before running the TurboTrain at high speed became uncomfortable, and later on impossible.
Obviously any high-speed rail in the U.S. will have to be run on a dedicated line. To make sure the ordinary railroad companies don't access and ruin it, it should be a different gauge or technology entirely. That's a whole new infrastructure: land to be purchased, bridges to be built, etc. all without disrupting existing rail service.
Nobody in the U.S. has the stomach for that kind of fight. The last such project - before the days of high-speed rail - was the "National Highway Defense System" - our nation-wide Interstate road network, and it took an ex-general with a personal interest in the matter to push it through. As for long-distance trains, we are still using the same right-of-ways that U.S. railroad companies purchased or were awarded up to 180 years ago!
