[ghaff]

>It would take a complete redesign of car interiors to something far more comfortable/secure for lying down but no reason that problem couldn't be solved.

Well, it's solved. They're called RVs. As a kid (or even as an adult), I think I'd still find it being pretty cooped up. It's one reason that I've never taken long-haul Amtrak that I suspect I'd find is more interesting in the theory than in the practice.

[Symbiote]

I've never been in an American RV, which I know are huge, but still narrower than a train. The ride on a train is usually much smoother than the best road, and of course you can walk around, use the dining car etc while the train is moving.

There are some pictures of various Amtrack train interiors at [1], aimed at tourists. That toilet next to the seat is weird, I think I'd prefer a shared toilet at the end of the corridor. But overall, the US has very spacious long-distance trains.

(I have taken one long-distance Amtrack train, for about 11 hours. The standard seat was as big as a first-class seat in most of Europe.)

[1] https://www.seat61.com/UnitedStates.htm