Sure, but they don't necessarily need such big ones. Big cars are primarily a consumer preference thing in the US rather than an actual need, and consumer preferences can change, both organically and due to outside pressure (the 70s oil crisis did reduce the size of American cars significantly, for instance).

Also, of course, bad mass transit is fixable. And potentially fairly cheaply; for the lowish density cities common in the US BRT systems would likely largely be fine.