The people of Bangor Maine and Buffalo NY have a hell of a lot more in common with the people of Cincinnati Ohio than they do with the people of Portland Maine and NYC.
On the west coast the "wealthy urban and suburban areas on the coast" vs "literally everywhere else" difference is even more stark. And I'm not talking about just the urban vs rural divide. The people of secondary cities resent being ruled by the interests of the major metropolitan areas as much as the rural folks do.
Cities/MSAs are the drivers of cultural identification in America, much less so than states.
Nearly 100% of Michigan is 150 miles or less from an international border that is in navigable waters. Is it a coastal state?
Navigable Waters of the United States has a specific legal definition [1] and it has nothing to do with whether it's salt water or fresh water. So the question of whether a particular state is "coastal" based on proximity to salt water a valid question!