If you look at places with nice public transit like Germany or Japan, they have much weaker freedom of speech and assembly laws so they can enforce the kind of rules private enterprises do in the USA. Americans, and I agree with them on this point, aren't going to weaken civil rights just because it would happen to make public transit more viable.
Private transport just has a lot of opportunities to deal with security or annoyance concerns you can't address with public transit. I don't think the opposition is so much to mass transit, just public transit, if the USA had something like the jeepnees they have in the philippines where I could pay $.25 to go across town and the bus driver can shove the assholes right off he bus, it'd be awesome.