Sure they can "work" in densely populated cities like the Eastern corridor. And I wouldn't even think of owning a car in NYC. But America is a BIG country, with stretches in the West where towns can be 100 miles from another.
I think you could ask the same question of Australia.
Trains I'm sure go through the big cities, but I'd be surprised if there's a whole lot of routes going deep into the bush.
Want to see Ayer's Rock? I've heard it's a great motorcycle excursion. But is there a train that goes there?
The Mount Washington Cog Railway in New Hampshire (still in operation) once connected to the Boston & Maine Railway. Nowadays, one can only drive to meet this train.
you can go by Ghan train to Alice Springs..