What you have to really ask is, what are americans willing to sacrafice in their daily lives if it really came down to it? Because a car is a necessity. I meant to say, people seem to think a car is a necessity.
If you take everything that's not an absolute necessity, then sumed it up, divided it by the amount of gas one uses, that is the cost of gas that's necessary to cause the public to give up the automobile.
I'm willing to bet people would give up cable tv, go to generic everything, wear clothes with holes in them, buy single ply, skip a meal a day, before giving up their cars.