It looks like Alaska is the most diverse when it comes to their soft drink names.
Or the sample sizes weren't very big.
Basically, around here:
1. "Coke" or "Pepsi" means cola drink. "Sprite" or "7-Up" means lemon-lime drink. If you ask for a Sprite and they have 7-Up, they might ask, but they'll give that to you.
2. "Soda" is the default, although people don't think of "pop" as sounding weird at all.
3. "A coke" can also mean a soft drink. However, if you ask for "a coke" some people may just get you a Coke, even if they have other things.