Whenever I hear someone imply (usually this claim is made by a Jeish man who never took civics) that this is a Christian country, I want to reach for a revolver. Fortunately, at DovBear we use words, not bullets, so take that, true believers.
* Our law isn't based on any Christian document, or religious document, including the 10 Commandments. Goverment and laws do nothing nothing to dissuade anyone from coveting anything they like, to name but one example. Most of the rest of the Commandments is either exclusively religious (and therefore not included in our statutes) or are included in one form or another in the legal code of every known human society, including many that preceded Christianity by centuries.
* The founders were not religious men. Though Jefferson and Washington were vestrymen in the Church of England, implying that they were not only believers but Christian activists, this was when there was no separation of church and state. If you wanted to be a community leader or if others expected it of you as a gentleman farmer, the church vestry was an essential part of the role. But Jefferson often praised the morality of atheists and Washington regulalry refused communion.
* The Constitution is godless. It's the first significant governing charter in the history of mankind that does not invoke any deities, even impersonal ones, for support. This can hardly be an accidental omission. Also, it was written at a time when Massachusetts established a specific church (the COngregationalists) and it replaced a document (the Articles of Confederation) which did mention God.
The framers understood that if any government enforces or even encourages any religious belief or lack of belief, everyone's religious liberty is put at risk. That's the basis of liberalism, and it's something a minority group like ours would be wise to remember.