You need density to support a train system. You need a large number of riders to make it economical and you need them living within a reasonable distance of the stations. The US is very spread out. You can blame cars for that but that is the world we live in. The US is also very big with large rural areas, the western US didn't even really develop until trains came out in the 1869. Europe was built around compact cities based on horses and walking long before cars.
I agree that we are too car focused and it has become a sort of arms race, build more roads, more cars, more roads, etc.