A few things...
The nation was founded on the principle of taxation without representation (funny now, considering the current status of the nation's capital). Church/state matters were secondary at best.
Jesus actually was black: I have yet to see a white person with skin of brass and hair like wool.
Kwanzaa is indeed based on African principles, but one of the main tenets of Afrocentrism is its focus on the collective: not the African collective, but the entire collective. Eurocentrism would happen to be the set of ideas with the top-down approach and all. It's kind-of like the "black lives matter" thing: non-black people often respond "all lives matter". Last I checked, black people were part of 'all', so there's that.
All that said, I agree that we've gotten way too PC with holiday wishes and all. If someone says "Merry Christmas" and you're not Christian, shut up and take it as positive - or at least conversational - message it was intended to be. Same with Hanukkah, Kwanzaa, Festivus, or whatever else.
One last bit: the racial stuff is nearing SW "I won't dance for so-and-so because" levels...and no matter what race we are, I think we can all agree that we don't want to be anything like them.