this is one thing i notice, and have alot during the travels racing this past summer.
dirty south it is coke-- say from georgia to florida, w/ lousianna/mississippi/alabam making the biggest contingent. nothing like getting deep fried crawfish and a “coke” at some hill jack gas station at 3 am.
west of pocconnos in pa/parts of ny, ohio and up into michigan it is pop.
every where else i have been it is soda.