That's crossing the west, or even the west of the west. Trains are slower through that section.

A 100mph train (again, not a modern high speed train) with limited stops would beat the car. Not sure the track could be built for this in this geography, however.

Yes, though the speed limit along the same stretch across Nevada is 80 mph, with the general flow of traffic between 85-90mph. Legality aside, the roads are very high quality and you can cruise along at 100 mph without much difficulty in a car.

100+ mph roads aren't unheard of (see autobahn). Neither are 100+ mph trains. The fact that neither is available is frustrating.