The first person I ever heard talk about the Coke / soft drink thing was Lewis Grizzard circa 1982. He wrote a piece about Yankees coming down south wearing black socks with sandles wanting a "pop." He always pronounced "pop" with a real nasaly accent.
Now I think we are fast becoming one big generic blob. We are losing more and more of our regional difference because we all see the same TV shows, and we can all buy the same products. I don't think that is really a good thing.