how come presidents can't amass the popularity of governors

[Nichlemn]

America has huge cultural divides, and political techniques that work in West Virginia do not work in very-different Virginia.

This. America is not monolith, while many states are.

Exactly - the cultural diversity across the country is far greater than the cultural diversity within any single state.

Is this really true, or are we just biased to think that bigger = more diverse? New York, for instance, is probably more diverse than the US if you're looking at divisions of proportionate size.