Russell Shorto gives a dispassionate and even-handed account in answer to the question, centering — of course — on the fundamentalist members of the Texas Board of Education.
The question, it seems to me, revolves around two definitions. What do we mean by Founders? If referring to the Puritans and Pilgrims, the answer is self-evident. But the Jamestown Colony preceded both of them, and while they were accompanied at some point by a chaplain (who baptized Pocahontas), their ambitions were notoriously secular. If the title is restricted to the founders of the nation, there is no doubt that they were in their own ways religious. But a fundamentalist of today might look askance of their idea of religion. What, after all, does it take to be a Christian?  To accept the Nicene Creed? George Washington would walk out of his Anglican Church every Sunday rather than recite it or take communion. To believe in the Trinity? John Adams, the Unitarian, didn’t believe in it, nor did most of his New England compatriots, nor did the Puritans. To accept Jesus Christ as one’s Lord and Savior? Jefferson snipped out the miracles from the Gospels to try, he said, to discover the authentic, human Jesus hidden by the god-worshippers.
The Founders were almost certainly 95 percent God-fearing Protestants, as Shorto says. But how Washington, Adams, and Jefferson would regard today’s fundamentalist sectarians, including Don McElroy of the  Texas Board of Education, is also fairly easy for me to imagine. As for Ben Franklin or Alexander Hamilton, don’t even go there.
One can pick and choose from the historical record to make one’s case, just as one can pick and choose from the Bible to make one’s religion. But in both instances, the conviction usually precedes the evidence selected to back it up.
