That's not a lack of cultural background, that's merely a lack of knowledge around who Benedict Arnold was, and apparently somebody doing you a disservice by ex

That's not a lack of cultural background, that's merely a lack of knowledge around who Benedict Arnold was, and apparently somebody doing you a disservice by explaining that it's a synonym for bad. If somebody had first explained to you that Benedict Arnold was a well known traitor during the revolutionary war you'd have nearly the same context as your average American. It's hardly what I would call untranslatable. I'm sure you could find some poor sod who the public education system failed so terribly that Benedict Arnold is as equally opaque in America.