Growing up as a Michigander, that's the term I learned for carbonated soft drinks. E.g., redpop: https://heartofmich.com/products/faygo-redpop
But I thought that was a pretty midwestern phenomenon. I thought the rest of the US was in the "soda" camp, except for the south, where I was horrified to learn that "coke" is the generic term.
And an extremely enterprising soul, Alan McConchie, has produced an excellent map confirming this: https://popvssoda.com/
So why is West Virginia talking about pop? It looks like WV is a linguistic battleground, with all three words having influence. But this particular thing is in an area I didn't know existed, WV's "Northern Panhandle", a territorial incursion which creeps up between Columbus and Pittsburgh. https://en.wikipedia.org/wiki/Northern_Panhandle_of_West_Vir...
And it turns out that goes back to the Revolutionary War, where Virginia, Connecticut, and Massachusetts all tried to claim parts of the Midwest: https://en.wikipedia.org/wiki/Illinois_County,_Virginia