Why can't the religious understand we live in a non-theocratic society?

Many very religious people have no wish to impose their religion on others, through legislation or otherwise. The U.S. is a little odd that way. American Christians are extremely political, for some reason, and find it hard to draw the line between their personal faith and their civic life, or to imagine living comfortably in a society with multiple belief systems. It is not a problem with religion per se, it is a problem with American-style Christianity.