1) Most Americans don’t live in “city centers”; they live in the “burbs”, so getting from the center city to where they live is an additional layer of access; this is slowly changing; 2) Long distance rail travel in this country can be very interesting, but it is also quite slow (real slow), so if you have a lot of time on your hands and don’t mind if freight gets a higher priority than you, have at it; 3) if you’re, for example, in my city and need to get to, say, LA, there are (very few) rail connections, but the better bet is to put up with the enormous hassle of air travel and just bite the bullet;The US of A is deciding whether it wants to build high speed railtracks. Currently it is in an impasse as your beloved President thinks it might be a bit pricey to build trains which run about 225kph, as opposed to the new Chinese trains which run at 400 kph.. With the price of Airlines, trains might seem dearer but, they deliver from city centre to city centre! Add the the times spent to travel from airport to airport and the difference will be negligable. Just build the lines!
On the East Coast you find high population densities which makes rail travel a viable and economic option, especially in the Boston-NYC-WashingonDC corridor.
When I was a young man, my family would go to the Houston airport to pick up my Dad (traveling from NYC to Houston) from Hobby Airport. Before going there, we would all “get dressed up” in our Sunday best. I can’t stop laughing at the thought of what happened to people “dressing up” to fly. It was a sweeter but more limited clientele that the airlines served at the time, before the advent of “discount” airlines.