The US may have a majority Christian population, but it was decided at the beginning that there would be no official national religion. The mother country, England, had an established religion (the Church of England), as did the Netherlands (Dutch Reformed), Scotland (Presbyterian) and Ireland (which was mostly Roman Catholic, but there were eventually two establish religions, Presbyterian in Ulster, and Church of England in the South) and nearly every other state in Europe.
The context of Europe and England was a series of bloody religious wars. In Europe these were between the Catholics and the Protestants, but England first had the Catholics duke it out with the Church of England (Queens Mary and Elizabeth) and later between the Caviliers (Anglicans) and then Roundheads (Cromwell's Separatists). The Founding Fathers decided that it was best to avoid this whole bloody shebang by agreeing to disagree as individuals and to keep the state out of religion. I think the Church of England was officially the established church of Maryland for a time, but it had no major effect on the state or the nation as a whole.
Who would the Founders endorse?
I think they would be baffled by the changes. I see Franklin and Jefferson avoiding the entire matter for several years until each got his website up. Washington would hardly be impressed by any need to keep troops in Iraq. He was very much in favor of 'avoiding foreign entanglements', and I don't see him having a high opinion of NAFTA or CAFTA.
I see them all as likely to have a deep interest in how Canada turned out.
Remember, about half of our founding fathers found slavery acceptable, and all found it tolerable.
