For the sake of brevity, I'll only mention a couple of points Jester didn't.
US is NOT controlled by bible-thumpers. Else we wouldn't have legal abortions, murder, sex, and obscenities on TV and movies, and lots of other stuff.
EVERY religion of any size has factions. Jews, Muslims, Hindus, Christians, Mormons, everybody. The more popular it is, the more likely you'll find violent wackos who don't get it but want to use it for their own purposes - Muslim terrorists, "Christian" clinic-bombers, and so on. Wearing the same label doesn't make everyone alike.
Quite easy to be fanatical about atheism. Such a person might get riled up everytime someone mentions God, for example. It's the "anybody but" syndrome, like why some people voted for Kerry.
(Aha! Full circle, back to election results topic!)