Definitely would say it's not a racial thing IMO. I'm from Western NY originally, and we *always* said "pop," I don't think I hardly *ever* heard anyone say "soda." Now that I live in TN, I find that about half of the people say "pop" and half say "soda." My impression always was that "pop" was a northern thing. Fascinating though how different the little things can be throughout the country.
