Please carefully read Article 6, paragraph 3 of the US Constitution. It's one of the clearest, and most obvious places where the founding fathers enforce the fact that we are a secular Republic, not a theocracy, and not a Christian nation.
The text reads , in part:
all executive and judicial Officers, both of the United States and of the several States, shall be bound by Oath or Affirmation, to support this Constitution; but no religious test shall ever be required as a qualification to any office or public trust under the United States.
The founders intended to ensure that even a Jew, a Hindu, or an atheist could hold public office. That has profound implications for our society as a whole