My view is that the auto industry has long and usually paid for itself as people buy cars (there was the 2008 bailout). For the highways, my understanding is that the Federally funded ones are paid for from the Highway Trust Fund which gets the Federal part of gasoline taxes. IIRC (I don't have good data) is that that fund is a favorite for raiding for money for other projects, maybe even trains.

So, I don't see cars as a scam. Passenger trains? Yes. Cars? No.