I didn't realize because the other stuff you said seemed kind of counter to what you said I mean you directly compared them to the British empire and Greenland and France, even though none of those places have American accents. I could see Cajun I guess if you focus on the fact that it's swamplands but then you said their clan name is wendigo, which is like the Northeastern native american folklore which makes me think of them being more like Algonquians. Then the civil war thing seems like a history misunderstanding.
Like I said I though I was never saying you couldn't do something just that I dislike it and they'd be the last race I'd give american accents and wouldn't really consider it unless the whole setting has those accents.
I mentioned because they have a similiar mix like how modern America is a mix of cultures that moved to the new world. That kind of cultural mix also caused me to imagine them having American accents. It's a fantasy setting so if you can imagine everyone in the European-styled region sounding American & the Elves as British I don't see why it can't be the otherway around. Also kinda makes Elves sound oddly exotic if they sound like a more modern culture compared ro everyone else who sounds like "old world" cultures.
The Wendigo is Native American yes but made me again associate them with Americans, but there Swampy habitat made me think more Louisiana (also I was kinda inspired by the Hewarzi Marshalnds of Diablo which was specifically inspired by it).
The civil war thing was more just about the cultural split. Let's ignore EVERYTHING about IRL civil war, heck I don't even know if the Elves had a civil war. It was more about the idealogical split between the race as "Dark" & "Hugh" Elves were considered the same people before the split. The Datk Elves (according to Tinkerer) were marked by there abuse of dark magic. I was more focused on the magic than anything else.
It was just how I see hear it when I read the lines. My headcannon, & I think we can all agree, that we can have our own headcannon. Unless Tinkerer himself tells us what accent is where we can just imagine what we want.