Amtrak is still a thing for passenger trains. It’s just that it’s slower than flying and just as expensive.

This is the core reason passenger rail has not become dominant in the US. The country is so physically large that planes do passenger rail's job, but faster and at the same price point.

Instead, rail in the US is almost entirely bulk cargo as that makes a ton of sense. Cargo trains are cheaper than trucks/aircraft and the slower speed can be easily planned for.