A UNITER, NOT A DIVIDER
On Volokh Conspiracy, Jacob Levy spots an interesting distinction in Democratic speakers' rhetoric:
First, and most importantly, this portion of Obama's speech was symmetrical with respect to partisan, cultural, and religious divides. It's "pundits" who seek to describe us as divided. But in fact, we're all red and we're all blue. Supporting the war, worshipping God, and playing Little League are symmetrical with not liking the Patriot Act, opposing the war, and having gay friends. That's very different from the "Those nasty conservatives are divisive, unlike us nice inclusive liberals" theme that's kept popping up.
Relatedly, there's something offensive in the "Take America back"/ "Let America be America again" stuff. It's something I fully expect to keep hearing; it's something I remember loathing about the first Clinton inauguration. It's the necessary implication that Republicans, and Republican government, aren't really American, that Democratic rule is not only preferable (of course Democrats think that) but the natural order of things, an order that must be restored (notice the restoration theme in both "take back" and "be America again"). Obama didn't imply any of that, either.
Finally, unlike Edwards, Obama's not imagining one America as some future state of affairs to be accomplished with a Democratic victory. It's a present state of affairs-- we are, already, genuinely united.
Come to think of it, the Republicans' cultural insanity in the mid-'90s had a "Take America back" quality to it. But America was feeling pretty happy and didn't want to go back.