Hard right paleo-conservative Thomas Fleming explains why America was not founded to be a "Christian Nation." He writes:
Despite the number of religious fanatics who landed on our shores early on, America has never been a Christian nation. Conservative evangelicals are fond of saying that the Founding Fathers were all pious Christians, but few of the men who led the Revolution or drafted the Constitution could be described as pious or even orthodox. George Washington was an ordinary Episcopalian who showed no conspicuous attachment to religion. His biographer Parson Weems has preserved touching stories about Washington’s faith, but Weems was a notorious liar, and his morale-building stories have repeatedly been debunked. The chaplain to the First Continental Congress knew Washington well and respected him, but, when asked in 1832 about the first president’s religion, he replied, “I do not believe that any degree of recollection will bring to my mind any fact which will prove General Washington to have been a believer in the Christian revelation.”
Revelation, miracles, and mystery were a stumbling block to John Adams, who was an undoubted Unitarian, like his wife, Abigail. Ben Franklin turned deist at the age of 15, before turning into a freethinker and Freemason. He was also a notorious philanderer who fathered bastards and wrote a famous essay on how to get and keep a mistress. Small wonder that Newt Gingrich says Franklin was “great in the way he lived his life.” Thomas Jefferson was also a mildly anti-Christian deist.
As Tocqueville told us 150 years ago, we are a conventional people, afraid of controversy. Going to church, in most periods of our history, has entailed fewer social complications than a reputation for atheism. No known atheist has ever been elected president: Lincoln learned to keep his skepticism to himself. America’s tradition of toleration—a peculiar blend of public hypocrisy and personal indifference to religion—is often explained by the First Amendment. Anti-American Catholics and ACLU liberals agree that the development of a Christian social order (much less a religious establishment) was prevented by the so-called wall of separation between Church and state. The phrase comes from a letter that Thomas Jefferson addressed to a Baptist association in Danbury, Connecticut, in 1802....
To be fair to that good man, Jefferson was in something of a bind. His indifference (at best) to religion was well known, and he knew that anything he wrote could and would be used against him by political rivals who had always tried to represent him as the enemy of Christianity. Cleverly, Jefferson did not even answer the Baptists’ main point: He wrote nothing about the rights of Baptists in Connecticut or the power of the legislature but spoke only of the national legislature—that is, the U.S. Congress—which is forbidden to establish a church or interfere in the exercise of religion.
Jefferson’s wall of separation cannot honestly be used to justify the government’s campaign to eliminate Christianity from public places. The President thought, rightly or wrongly, that he was merely restating and applying the Free Exercise Clause of the First Amendment, which says: “Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press, or of the right of the people peaceably to assemble, and to petition the government for a redress of grievances.”
It is not easy today to get the point of this clause, since so few of us have lived in a country with an established religion....
The First Amendment, then, forbids Congress either to establish a national church or to interfere in the exercise of religion. Why Congress, specifically? Because Congress, elected from the people, is the supreme lawmaking body. As Jefferson understood, it was up to Congress to pass laws, which the president executed. The president could not have his own policies on religious freedom any more than he was entitled to have his own policies on war (much less the special “war powers” that Lincoln invented and subsequent presidents have abused): For a president to impose his own ideas on the nation would be tyrannical. Nor did anyone (except possibly Jefferson) ever think the federal courts would get involved in such an issue, since their role was to interpret the Constitution and federal laws, and they had virtually no authority to intrude themselves into the affairs of the separate sovereign states.
The fears of the Danbury Baptists were legitimate: Under the First Amendment, the states could, theoretically, interfere in the exercise of religion or establish a church, whether Anglican or Congregationalist. The fear of a national establishment came natural to Americans. What sort of national church could America have that would unite the Anglicans of Virginia and South Carolina with the Puritans of New England and the Quakers of Pennsylvania? Even the Southern states were religiously diverse. The Carolina backcountry was dominated by Presbyterians and, eventually, Methodists, Baptists, and Campbellites, while Charleston had a significant Catholic population even in the early 19th century, and eventually the number of Irish Catholics in the lower South and, after the Louisiana Purchase, French and Spanish Catholics in Louisiana was too great to be ignored. So, although Christianity held a privileged position, it was, for practical reasons, virtually impossible for states to maintain a church establishment.
Although the Bill of Rights is interpreted today as a guarantee of individual and minority rights to exercise freedoms of expression and religion, this was not the original reading. In this respect, Jefferson’s letter points in the wrong direction. The primary object of the Bill of Rights was to restrain the national government, particularly the Congress.