America's gov't-religion connection is, like our views of race, weeeeird. Why is the movie 'Balls of Fury' even remotely acceptable in this day and age, when it's filled with ridiculous Asian racial caricatures? The answer 'because it's a parody of martial arts movies, not a parody of Asian-American culture' is either nuanced or tortured logic, depending on your point of view, but it's something Americans get in their gut.
Likewise, why is it ok for existing versions of the 10 commandments to reside in courthouses when new ones can't be built? Why is it ok for Christmas to be a federal holiday and our money to say 'in God we trust?' The answer that the old ones are ok because they're grandfathered probably doesn't hold much weight in other countries but again, makes total sense to us nutty Americans.
Maybe the fact that religious types in America tend to think they have a lot in common with each other ('cept for those Muslim heathens, of course) has a lot to do with it. I can't think of many countries where Mitt Romney could make a speech that says Mormonism is a friendly brother to Christianity to the heads of the Christian conservatives and not be laughed out of the room, but he did-- and they loved him.