Well, look at it this way: America is the sum of all Americans, but it is also the Constitution as written by the Founders.
see what I mean?
I see what you're saying, and it's true in theory, but in practice, it's today's people who make the difference. On paper, we have the same Constitution that we've always had, but the Founders certainly wouldn't recognize today's government as what they "contracted" for.
Same with the "original principles," if any, of the Democrat Party. I don't like to be uncharitable about Zell Miller, but he sounds like he's letting sentimentality cloud his judgment.