I recently needed two tickets from NYC to LA, and was astonished to find air tickets for $80 and rail tickets for $2200. It's so unbelievably expensive (not counting that the flight was a few hours and the train was 56 hours).

Very disappointing! How is it so expensive?!

Competition, I suppose. Still, that seems extreme. A few years (might have been eight) back, I traveled Amtrak's Zephyr from Chicago to California. The roomette for two (coach would have been cheaper) was some $450, about the same as 2nd class air fare for one then. But yes, the train isn't in a particular hurry, expected travel time is some 50h, but 1.5h in, it was already 20m late for no apparent reason. Most passengers were tourist, but I also talked to a fellow who was going to California to pick up a used car for his daughter.

I like the idea of long distance train traveling, as one can get off and back on later (check the fine print of your ticket though). Apparently, that's not customary however and earned me an interview by a TSA agent (a very polite fellow, odd as it may sound) who approached me (with a local Sheriff in tow) at a scheduled stop.

Fair. I've had one flight to the UK that cost less than the train ticket from the UK airport to my actual destination. Air tickets got a lot more expensive after the pandemic, but it's still close.

(OTOH, I've also had one case where it was cheaper to take the ferry and trains back from the UK to Berlin than fly, presumably because of massive demand as that was the day Stansted airport was closed by 1cm of snow and I had an 8 hour queue for a replacement flight that was itself also cancelled).