How many Americans actually fly, though? I think people forget that a lot of us aren't opting out of the body scanner simply because we don't travel often enough or far enough to be at the airport (or not very often) and we prefer to travel by automobile.
I think we would find, if we commissioned a study, that people who are most prickly about their individual liberty, or most resistant to strip-searching and body-scanning; are people who don't want to be in a crowded airliner fuselage anyway. Us curmudgeonly sorts prefer the open road, and only travel by airline if the benefits far outweigh the costs.
It could also be a matter of tax bracket.