we talked about this in anthro class. This happens a lot in countries, one part of the country dominates it culturally wise and it expands. We also talked about this in Geography. lol
Examples in the states would be the Philly cheese steak, doughnut (east coast), brat(mid west), deep dish(east) pizza and thin crust pizza(midwest) and buffalo wings(east) and coffee houses (west coast).
Then nachos (southwest), angus steaks(plains) and so on.
Cultures aren't just limited anymore to a certain area. Hence the popularity of Eh? poutine, etc. across Canada.