The freight railroads aren't good at what they do. It would be much easier to run passenger services (and improve their own operations) if they ran trains that actually fit within their own passing loops, but they desperately want to reduce the number of people they have to pay to run their trains. Both would also benefit from better maintained infrastructure with upgrades such as electrification and more double tracking, but the railroads don't want to spend any more money than absolutely necessary to keep their (mostly) running.

Sounds like you've never participated in civil disobedience. Shame.

The railroads should be nationalized and new ones built over highways.

Because the USA is 2892 miles wide. Even a 285 mph bullet train, which is the fastest train in the world, would take 10 hours to cross the United States, and that's at absolute max speed, with no stops, which isn't how trains operate. Realistically it would take a few days to cross the United States, as opposed to 5 hours in an airplane, or a couple of hours in a hypersonic jet. Trains are great, especially for more relaxed travel, or moving lots of goods, but they're not a final solution for countries this size.

Efficient High-speed rails are already possible and have been since the 70s, it's not a lack of science that stops them from being a thing, it's a lack of desire from government officials being paid by private interests to do things less efficiently because people are getting paid.

Still, someone has to finance it. In the worst case you have a high speed rail network with high operationg costs that nobody uses, but taxpayers still need to maintain.