I don’t think most people including those from the area would even associate the name with French, so there isn’t the same intentionality. It’s the same with indigenous language-origin or Spanish-origin place names in the US/Canada, our place names in general that are often centuries old and conceptually separate from their origins, and feels quite distinct from intentionally trying to emulate a foreign language pronunciation for one language but butchering words in another language (not that that’s unique to the UK).

I didn't know Detroit had French Origin.

Spanish slang from the 90s in my country imported Detroit and Spanish-ized the pronunciation as ditroy.

Since it has the same consonants as detrás, Spanish for behind, it can be used a a synonym for behind and also as an euphemism for the behind part of the body.

Yes but for an unknown reason Des Moines was not completely butchered

"Foyer" is the classic example.