In the case of the UP, there is an ongoing battle with Amtrak. Schedules are never met, diversions of passenger traffic to busses is common, and generally they don't get along.
The BNSF, on the other hand, mixes the Amtrak traffic in with the freight traffic and provides reasonably good schedule predictability. The BNSF also runs some passenger service in the Chicago area.
The U.S. west was populated entirely after railroads were invented, so practically every town and city has vestiges of a rail system still in place. It would not be impossible to get the American rail system back to the point where it was in the 1920s when it peaked.
That's not exactly the same as a modern high-speed rail system, though.
