I can't think of any topic of civic discourse in the last 50 years that has been more pointless or that has provided the opportunity for the parading of more ignorance and ill will than the question of whether the United States is a "Christian nation." Particularly discouraging has been some right-wing demagogues' portrayal of the Founding Fathers as more or less a collection of Billy Grahams in powdered wigs.
Now, finally, someone with some knowledge of the subject and a dispassionate interest in judging the matter accurately has turned his attention to what Washington, Jefferson, Madison, Franklin, Hamilton and all those other guys on various denominations of U. S. currency actually believed. The results are not particularly surprising to anyone who has studied American history, but they should still be an eye-opener to most Americans -- both left and right.
Bottom line: The Founding Fathers mostly believed in God (if only the God of the Enlightenment), which puts them at odds with most of the secular Left. But relatively few of the Founding Fathers believed that Jesus was the divinely begotten Son of that God, which puts them equally at odds with the Christian Right.
Read the fascinating details here.
(By the way, one curious omission from the First Things review (although I hope not from Prof. Holmes's book itself) is Charles Carroll, the only Catholic signer of the Declaration of Independence and the first great Catholic figure in the history of the new Republic. A wealthy Maryland farmer--and slave owner--he nonetheless advocated a gradual end to slavery, introducing abolitionist legislation in the Maryland senate and promoting the establishment of Liberia as a nation home for emancipated and "repatriated" slaves. That makes his beliefs with regard to "America's original sin" considerably more admirable than those of most of his fellow Founding Fathers, especially the slave-holding ones.)