I don't agree with those who say America is a Christian nation, but
I'll concede that no non-Christian religions were professed by any of
our founders.

Oh so absolutely not true. :-)

But in the spirit of the times, many used Christianity as a "beard".

Many of the founders were deists, animists, etc. Nearly all were far more into
Masonry than Christianity. One philosophy does not automatically preclude the
other, but neither does it automatically include it.