Supposed to be? According to whom? The founders clearly defined that there would not be an official national church. If you mean that at the time of its founding most citizens identified with one Christian sect or another, that would be true.
Well, Truthisobvios beat me to the Treaty of Tripoli thing (ehh, I've been practicing guitar a lot, that takes up a lot of time). Seperation of church and state is a wonderful thing. So is the right to believe whatever religion you want. My opinion is: I may not agree with your religion, but I would fight to the death for your right to believe what you want. It's a big thing and it's great for us. Religiously run countries don't work out very well (the middle east as of now is a perfect example). Our government is supposed to be as secular as possible.
No. Not in its philosophy, or in what it loves, or in what it does. Despite its Judeo-Christian roots and heritage, and the beliefs of some of its founders, the United States today is a nation that follows other gods, and lives a lifestyle that is not compatible with Christianity. Since its beginning, America has been deeply influenced by the Judeo-Christian tradition and by the teachings of the Bible. Some of our earliest settlers (such as the Pilgrims) came here for religious reasons, convinced that God was going to give them the opportunity to worship Him in freedom. Our legal system was largely built on the Bible's teaching about right and wrong, and our forefathers took seriously its statement that "Blessed is the nation whose God is the Lord" (Psalm 33:12). At the same time, not every citizen at the beginning of our nation was a committed Christian, nor are they today. In fact, some today even want to banish all mention of God from public life-something our nation's founders never intended.
"As the Government of the United States of America is not, in any sense, founded on the Christian religion; as it has in itself no character of enmity against the laws, religion, or tranquillity, of Musselmen; and as the said States never have entered into any war or act of hostility against any Mehomitan nation, it is declared by the parties that no pretext arising from religious opinions shall ever produce an interruption of the harmony existing between the two countries." [bold text, mine]
Click here to see the actual article 11 of the Treaty