I am religious but I am not Christian, true. I happen to be Jewish.
While the Founders would agree with you about moral issues and the moral fibre of the country, they wouldn’t be in a vacuum. 2014 is very different from their day. If they were versed in society today, and how secular it is, they would have to encompass those Americans as well,if they truly believed in the Constitution.
Gd has made it possible for people to not believe in Him. He has given us choice, and some have turned from Him. And according to our law, that is perfectly fine - to worship Him in their own way, or not to worship.
They would have a hard time with an openly gay Wiccan. But the a Constitution is based on principles that don’t necessarily have to stick only to what you believe.
Also, do note that Jefferson and others were also judeophiles and did base some of their writings on Judaic scholarship as well. It wasn’t strictly Christian.
Since you are not Christian, I see now why you have no problem with the anti-christianism I mentioned (my comment about Christians being in the crosshairs), nor any problem with the Tea Party’s exclusion of social conservative issues.