America is not a Christian nation
the American government, just like every true democracy, is secular. The term "secular" means it does not officially endorse any religion. This is in contrast, say, to Tudor England, where the Church of England was an arm of the government, or Saudi Arabia, where the penalty for apostasy is death. Technically, a country cannot even claim to be a democracy in any sense of the word unless it is secular. The founding fathers were a diverse bunch, some were atheist, some were agnostic, some were Christian, some of them positively hated Christianity, but all of them agreed on the principle of secularism, as shown by the Treaty of Tripoli. The US government does not technically endorse any church, mosque, temple or any religious organization (this is why they all have tax-exempt status but cannot recieve government funding).
I laugh when Christians say that America is a "Christian nation". It is true that Christians make up a majority of Americans, but that is precisely akin to saying that America is a "white nation" because whites are a majority. The American government does not (or at least, should not, to claim to be a true democracy, have any religious affiliation. If every member of senate was a Bible-thumper (oh...wait, they are!) it would still be irrelevant, so long as the First Amendmant (guaranteeing freedom to and from religion) remains in place (lets hope so) America is a secular country. To say that America is a Christian nation is to say that it officially endorses a Christian church. Fortunately, it does not. In the horrifying event that the United States Government had an arm entitled The Office of Christian Evangelism, and the United States Criminal Code was replaced by the Bible, the Department of Agrictulture was governed by Old Testament Crop laws, and the National Academy of science endorsed creationism (the NAS has 800 of the world's most respected scientists, it's current head, Bruce Alberts, first taught me molecular biology, and the chance of the absurdity I am suggesting is roughly akin to constructing an Ice palace in hell, so don't worry).
This would be precisely akin to the arm of the Saudi Government which is responsible for the enforcement of Islamic dictatorship, and the existence of Shar'ia Law courts, where the Qur'an and Hadity are the official and final arbiters of judiciary in Saudi Arabia, Oman, Yemen, UAE and Iran. If this was the case, only then could America be called a Christian nation.
"Physical reality” isn’t some arbitrary demarcation. It is defined in terms of what we can systematically investigate, directly or not, by means of our senses. It is preposterous to assert that the process of systematic scientific reasoning arbitrarily excludes “non-physical explanations” because the very notion of “non-physical explanation” is contradictory.