When seen from the outside, the U.S. is often viewed as a homogeneous place. Non-Americans have remarked to me about how great it is that in the vast area of the U.S. one needs only a single currency and a single language. While the currency advantage is indisputable, anyone who has traveled in the U.S. will tell you that, even setting aside recent immigrants mother tongues, regional linguistic differences can present a challenge. My eldest daughter has moved to an area of the country with which she had been previously unfamiliar. Among her accounts of the different weather and geography, she mentioned some linguistic differences. She admitted that she had anticipated some differences in accent, she had not anticipated certain vocabulary and usage differences. To my surprise, the one that annoyed her the most was their usage of "pop" for common carbonated soft drinks. In her experience, such things were always called "soda."
"'Soda' actually describes something in the drink," she asserted. "'Pop' is just an onomatopoeia. Just barely a real word."
As a certified old geezer (I have a child who has finished college and moved away), I was well aware of the "Pop" vs. "Soda" split, having had it brought to my attention when I traveled to Iowa as a boy. In fact, in 1996, there was a article on the subject written by Luanne von Schneidemesser, PhD in German linguistics and philology from the University of Wisconsin-Madison and senior editor of the Dictionary of American Regional English. In fact there is a web site devoted to the subject, and a U.S. map, derived from survey data from 2002 was available:
What surprised me about this map was how widespread the "coke" area was (I had previously assumed it was pretty much a Georgia phenomenon). Also of interest was that certain areas still called the soft drinks "dope," probably harkening back to the time when there was real dope (cocaine) in some soft drinks.
Information taken from 308 - The Pop Vs Soda Map
and The Pop vs. Soda Page.