That's a falsehood taken as "truth" by far too many.
In the chain of human events, the birthday of the nation is indissolubly linked with the birthday of the Savior. The Declaration of Independence laid the cornerstone of human government upon the first precepts of Christianity. -- John Quincy Adams
As to Jesus of Nazareth, my opinion of whom you particularly desire, I think the system of morals and His religion as He left them to us, the best the world ever saw or is likely to see. -- Benjamin Franklin
The Bible is a book worth more than all the other books that were ever printed. -- Patrick Henry
I do not believe that the Constitution was the offspring of inspiration, but I am as satisfied that it is as much the work of a Divine Providence as any of the miracles recorded in the Old and New Testament. -- Benjamin Rush
Whatever makes men good Christians, makes them good citizen. -- Daniel Webster
Read the quote by Franklin. He is showing respect for religion but no biographer would ever suggest he was a christian. Likewise the quote by Jefferson who was less agnostic than Franklin but nevertheless “not” a traditional christian.
There was tolerance and respect for those with different beliefs in those days.