If there were high-speed trains that could make cross-US trips in, say, 15 hours, and at comparable or cheaper cost vs. airplanes, I can imagine there might be

If there were high-speed trains that could make cross-US trips in, say, 15 hours, and at comparable or cheaper cost vs. airplanes, I can imagine there might be demand. I would be willing to take those overnight. But even if we could replace most <500 mile flights along the most popular routes (starting by connecting cities up and down the coasts), it would be a huge win as far as fuel economy is concerned.