Here is an interesting article about the faith of America's Founding Fathers: God and America’s Founders: Religion’s Role
We are not, nor have we ever been a Christian nation. We have been founded on religious principle, but even our Founding Fathers were ambiguous about their faith.
I read a biography of Benjamin Franklin a few years ago. In it he said that the council refused prayer because they could not afford to pay a chaplain. He was also quite free with the ladies.
Religion and politics should never be combined. We have seen some dangerous things in the church because of politics. Only god is able to save us, and He gave us Jesus Christ not politics.