"The founders were all devout Christians."
The Founding Fathers held a wide range of religious views, many of which would disqualify them from mainstream Christianity today. Thomas Jefferson literally cut the miracles out of his Bible with a razor, producing the 'Jefferson Bible' that retained Jesus's moral teachings while removing the virgin birth, resurrection, and all supernatural claims. Benjamin Franklin described himself as a deist who 'doubted' the divinity of Jesus. John Adams was a Unitarian who rejected the Trinity. James Madison opposed government chaplains and publicly funded religious displays.
The founders' religious diversity was not incidental — it was the reason they insisted on church-state separation. Many had witnessed or studied the religious wars that devastated Europe for centuries. They understood that government endorsement of any religion inevitably led to persecution of dissenters. The First Amendment's Establishment Clause was not written by atheists trying to suppress religion — it was written by people who understood that government and religion corrupt each other when they merge.
Some founders were indeed conventionally religious — Patrick Henry and Samuel Adams were devout Protestants. But the founders who wrote the Constitution and the Bill of Rights — Jefferson, Madison, Franklin, Hamilton — were overwhelmingly influenced by Enlightenment rationalism and religious skepticism. Claiming they founded a 'Christian nation' requires ignoring their own words, their legislative choices, and the document they produced, which mentions God exactly zero times.
The only reference to religion is the First Amendment's prohibition on establishment