I’ve been on a flight between Berlin and London that cost less than an Amtrak return ticket from Davis to Sacramento, and I’ve also been on a multi-day road trip from Davis to Salt Lake City that, while fun, was only a good financial choice due to four people squeezing into a Prius.
While I enjoyed camping and seeing bits of the US that foreigners like me don’t normally see, it’s not entirely clear that the difference between that and flying makes flying the luxury.
In general flying is more expensive in NA because of less competition and bigger distances. That's what I noticed when I moved from Europe to here. Now you have to take expensive tests to fly international both ways. That's why I consider it a luxury.
While I enjoyed camping and seeing bits of the US that foreigners like me don’t normally see, it’s not entirely clear that the difference between that and flying makes flying the luxury.