The American Founders, of course, wanted to leave all those messy, bloody sectarian battles back across the pond, and so, eventually fashioned a Constitution that glossed over the details bigtime.
Still, if "Christian" is nettlesome enough, what is a nation? A quote from the very wise man who is best known as the former occupant of Hillary Clinton's Senate seat is making the rounds again these days, and for good reason.
"The central conservative truth is that it is culture, not politics, that determines the success of a society. The central liberal truth is that politics can change a culture and save it from itself."---Sen. Daniel Patrick Moynihan (D-NY)
What is a nation, its government or its society? Most of the disputes, both on this blog and in current affairs, stem from fundamental and philosophical disagreement on the answer to this question.
[No, "both" is too squirrelly an answer.]