Your country was NOT founded on religious beliefs, and anyone who tells you so is lying. The founding fathers are a product of the Enlightenment, a strongly anti-religious (or anti-organized-religion) movement which directly fought against a king's "God given right" to rule. You see, kings used to justify their rule on them being chosen by God to be king. French (Oh no!) philosophers were completely against this idea and realized that God has nothing to do with effective government of any country.

The founding fathers are simply the first to apply French Enlightenment philosophy in a practical setting, and the French followed soon after (1789). Sure, they use "religious" languae sometimes in their documents, but that was simply the language of official documents at the time.