The American founding had a number of novel things to it. Though it wasn't entirely novel. For instance, the American Revolution wasn't quite as novel as say, the French Revolution which it inspired. On religion (correct me if I am mistaken), every single modern Western European nation state at the time was in some way formally connected to an official Christian sect.
At the state level, America post founding still retained some "state established" churches, which were on their way out.
at the federal level, there was nothing. George Washington, America's
first President, was like many founders, formally/nominally affiliated
with the Anglican then Episcopalian Church. "The Church of England"
against which America had then separated.
Washington spoke to the different religious "factions," he had a method
of seeming to be all things to all people. For instance, recent events
remind of us of Islam's place in the mind of America's founders. With the
assistance of his Secretary of State, Thomas Jefferson, Washington delivered remarks to Morocco where he claimed to "adore" (his word) the same God as the Muslim leader.
one could write this off as something "diplomatic." Perhaps it was.
It's certainly the kind of sentiment today that leaders in pluralistic
societies use. But back then, before America, every single head of state
was connected to an official church. And it was expected that in their
public utterances, they would endorse that particular brand of faith.
Not generic, bridge building, monotheism.
something that arguably Washington and the other early American
Presidents invented. And perhaps they were so effective at it because
such a sentiment mirrored their privately held religious convictions
which focused more on commonly held doctrines of monotheism and virtue,
while if not downplaying, outright removing other more divisive sectarian "doctrine."