About two years ago I moved way up north to Birmingham, AL from southern Louisiana.
I like ketchup with fries. I'll eat ketchup on a burger, but prefer sliced tomatoes. I slop the mustard on, but can't take mayo on a burger, much preferring horseradish instead.
Oddly my mustard Mayo decree is more Deep South and from black cooks
Mid south Nashville where I am now it’s not as common
For me the south starts when I cross the Tn river on eye sixty five headed to Mississippi
North Alabama is much more southern than Nashville
Same when headed west on forty
West tennessee is like Mississippi
West side of same river