I don't pay much attention to Dee Lusby's maps (in the US context).Many years ago Dee Lusby posted a map about cell sizes. Let us take worker brood cells only. The jest of the map was that the further north and higher the altitude the larger the brood cell. It has been many years since reviewing the map and my memory maybe faulty, but the Canadian border had cell sizes in the 5.1mm area and the Deep South was 4.7 to 4.9 mm.
All beekeeping is local. That is the problem with people from all over the continent commenting on cell size. It varies.
Massive and sustained migratory bee moves pretty much invalidate it.
In the US context, this is pretty much meaningless since locally adapted and stable bee sub-species never formed yet (IF ever will with all the bee moves).
Just now the local seller is selling tons packages from South to the locals here (the annual event in my town).
Talking of Canadian border bigger cell sizes vs. Deep South smaller cell is not much a factor because of this (in the US).
So the geographic location is not a strong factor.
The geographic locations did matter in the historic origins of the bees in the historic sense (pure black German/Russian bees are large; pure gray Caucasians are mid-size; etc).
Still do now, but somewhat washed out due to bee migrations and long distance sales as well.