Do you call it "pop"? "soda"? a brand name soda pop? I ran across a linguistics map showing who calls it what:
Read about it at the Strange Maps blog, The Pop Vs Soda Map. They cite an article by Luanne von Schneidemesser, PhD in German linguistics and philology (University of Wisconsin-Madison) showing who calls "carbonated beverages" what. They note that von Schneidemesser is a senior editor of the Dictionary of American Regional English.