Americans need to embrace public transit. We need trains that don't completely suck in both speed and schedule reliability.
We're never going to convince a lot of folks to leave their lifted F-150 or massive Suburban behind for a small car. But quality, affordable public transit that is not only efficient but saves money over owning a car would actually make a difference. We're more likely to be able to get people to just leave the F-150 in the driveway and eventually move away from it.
Much better for the environment, too, and reduces traffic / congestion, etc. I agree smaller cars would be good, but the goalpost should be getting away from the automobile.