How do you refer to soft drinks? Do you call them "Soda?" "Pop?" "Coke?"
Typically, this is a regional choice. Growing up (mainly) in the south, I just assumed everyone ordered a "coke." Then you specified what kind of coke you wanted. However, as I traveled around, I realized people actually use the terms "soda" and "pop."
Finally, someone has taken the time to compile data on this matter of national import. Check this out.
You can mouse over the little boxes below the map to see the distribution across the map. Here's another version, that looks more like a "county by county" political map.