Not gonna happen. Many of the most flown routes are from the NE to CA, a good 3,000 miles. That takes something like 5 hours in the air. NYC to LA takes 4 days on Amtrak. (Assuming it runs on time, which if it ever happened would be major news.)
Rail works well in Western Europe, where distances between cities are much smaller.
I've taken Amtrak 4 times from the Midwest to the West Coast. Oddly, every single time they have been EARLY....sometimes, the train actually parked for awhile to avoid being too early for stops. I swear from all of the stories that I've heard, I must be the only person who has experienced this level of service.
I agree WRT the longer cross country distances. But there are other choice routes. Another notion: A single transcontinental high speed route, NY to LA, only faster than any other railroad in the world. Faster than jet. Nuclear and magnetic technologies pressed into service. Maybe no rails, but a tube similar to pneumatic.