I beg to differ. Have you read the quotes by our forefathers? They were very religious, or at least strong in their belief of God. Plus they expressed the importance of its existance in society.
Some of them may have leaned towards Deism, though I never found any evidence of that. Being LDS, though, I could certainly understand such a leaning, because in their day, it was largely true.
Here are some quotes from Thomas Jefferson. I'll let you judge whether or not you believe that he was a devout Christian.
"The whole history of these books [the Gospels] is so defective and doubtful that it seems vain to attempt minute enquiry into it: and such tricks have been played with their text, and with the texts of other books relating to them, that we have a right, from that cause, to entertain much doubt what parts of them are genuine. In the New Testament there is internal evidence that parts of it have proceeded from an extraordinary man; and that other parts are of the fabric of very inferior minds. It is as easy to separate those parts, as to pick out diamonds from dunghills." -Thomas Jefferson, letter to John Adams, January 24, 1814
I never submitted the whole system of my opinions to the creed of any party of men whatever in religion, in philosophy, in politics, or in anything else where I was capable of thinking for myself. Such an addiction is the last degradation of a free and moral agent.
-Thomas Jefferson, letter to Francis Hopkinson, March 13, 1789
Among the sayings and discourses imputed to him [Jesus] by his biographers, I find many passages of fine imagination, correct morality, and of the most lovely benevolence; and others again of so much ignorance, so much absurdity, so much untruth, charlatanism, and imposture, as to pronounce it impossible that such contradictions should have proceeded from the same being.
-Thomas Jefferson, letter to William Short, April 13, 1820