Isn’t the obvious answer that many would refute the premise of meaningful regional variation? In which case the claim isn’t that somewhere else is that place but rather than all places are substantially equivalent on this difficult to measure concept (or difference is unknown).

Meritocracy is not a single thing. Regions do not have a uniform relationship with merit, as they are made of many different communities all living amongst each other. "Which is the most meritocratic part of America" is not even an especially meaningful question.