Where I grew up in Kansas, the generic was always pop, for any kind of flavored carbonated drink. Soda was unflavored and unsweetened, like "club soda" which is just fizzy carbonated water. Think "Scotch and soda." Or, an "ice cream soda" which is ice cream, soda water, and (usually) some flavoring such as chocolate, butterscotch or strawberry.
Here in Massachusetts it's soda.
But also here in New England they serve frappes, which are called a milkshake, shake, or malt anywhere else in the country.
Another Southernism, like coke instead of pop or soda, from my cousins in central Alabama, is the term
"chasing cock."
In Kansas (and Massachusetts too) it would be chasing girls (or chasing pussy.) But in Alabama, boys out chasing cock
is not a homosexual activity.
Lindy