Founding Fathers were Deists

You and most Americans have an abysmal ignorance of history. The Founding Fathers were Deists, almost to a man, and some of them hated Christianity (Adams and Paine immediately come to mind). You probably don't even know what Deism was and why it died out.

Washington did go regularly to church, probably for political reasons, but never took communion. Most of the rest used "God" in their vocabulary now and then, but this refers to the "Nature's God" of Deism -- something people read in those documents utterly without noticing or understanding.

This is because the Founding Fathers were an educated elite, and most of the educated elite back then were Deists. The rest of the population were of an assortment of religious views, ranging to the tolerant Quakers (whom Franklin admired and contributed to but never joined) to the intolerant Puritans and Catholics.

The unfortunate thing is the Founding Fathers were influenced by the Roman Republic, and designed their system a lot like it, with checks and balances and general elections and so on. As a result, after the founding generation passed, the religious types took over, and the US has not had a really great president since (except of course Lincoln, who seems to have been an atheist, but kept his mouth shut).