But are they truly "Christian" principles?
What about that bit about giving to Caesar what is Caesar and to God what is God's?
Now God may well ordain US-style federalism and separation powers as his ideal form of government. I have no clue what God ordains.
But I do think God would have trouble with even Washington and Madison, or Luther and Calvin, much less Pat Robertson, D James Kennedy, ordaining their constitutional vision as His.
Do I think the founders thought they were doing God's will? Yes, and I'd quote the Declaration just as you have for that proposition.
Do I personally think much of the American system is consistent with "Christian principles" in a way that the alternatives are not? Yes, again.
Do I think that said consistency is one of the big reasons I consider the Madison/Jefferson/Washington vision the best system of governance ever put into practice, perhaps the biggest reason? Yes, a third time.
But I also think that when we argue about how "Christian" the basis for the original vision was or was not, we miss Christ's main point. His desire for us is not to come up with the best government system in this world. His desire for us is even less for us to choose our government because of whether our forefathers, who we admire, believed in him or not.
His desire for us is to cast off our need for governments and other non-divine institutions, to trust in him first, last, and always. His desire is to listen to Him and listen for his guidance. We should not base our decisions or beliefs about proper government on "our" principles, but on His.
The question isn't whether American government should be based on "Christian" principles. It's whether it should be based on Christ's principles.
These are *not* the same thing.
And do not be conformed to this world, but be transformed by the renewing of your mind, that you may prove what is that good and acceptable and perfect will of God.
Romans 12:2 (NKJV)