Long distance train rides are incredibly expensive in the US.

Trains also do not have to completely supplant cars to make a difference. If people take the train to work and use their cars to run errands around town it's still an improvement over driving everywhere.

That's only helpful if they mostly share the same route; if it's a star topology, trains won't help.

Even shared bus services can made into something desirable with the right marketing and investment. The large tech companies provide luxuary coach services with WiFi to their workers and the people riding them are seemingly very happy with the services.

Metro service is the key. When frequencies get high enough the timetable exists only for the benefit of the operations personnel, customers don't care about it because their experience is like with an elevator. You don't ask for a timetable for the elevator, you just go to the place where elevators arrive, and wait, and very shortly there will be an elevator.

Very high densities are both the problem and the solution. They're the problem because under very high density private car ownership is infeasible, and the solution because public transport becomes fast and affordable. If you let it.