It is historical revisionism to say that the USA was not founded on Christian principles. The Revolution against the English monarchy was made up of many people so there were people such as Thomas Paine, now discarded.
Perhaps the historical revisionists are trying to say that Americans have no God-given rights.
So, you want to ignore Thomas Paine? On what basis? Because he doesn't fit your philosophy? You would have loved Jefferson. He literally ripped out pages of the Bible that he didn't agree with. You can find a copy of Jefferson's bible on the link I posted previously. But Jefferson wasn't a Christian and neither was Washington so you'd want to take them out of the history books as well. By the way, Ben Franklin was also a theist so you need to take him out as well. Ask yourself this question. Who is it that practices historical revisionism? The Radical Right of course.