That's why in my initial post I wrote "america's" but since he's american I was speaking on why he'd ask in that way.
Sure they use the rhetoric, but I wouldn't call it racist. Xenophobic perhaps or a way to try to demote your status in the country, but I would just say Cameroonian-French. To display your ethnic background and your nationality. Saying just french is kind of corny when you're merely 1-2 generation apart. It almost makes it seem like you're ashamed.
Again, you gotta understand the french context to know why she could be pissed at that question. I'll keep repeating myself, but this is what white french racists do all day everyday, from casual talk at work all the way up to media and the government. It's a well-known trick to show that those french people "aren't really french" (meaning : second-rank french) and is common knowledge among all non-white people here and people who study racism. Breh had no idea about all that and walked in naïve and oblivious of the situation of the country he's in. And obviously couldn't fathom that the issue might have been with him as opposed to with her, who has to deal with this bs all the time and doesn't want to deal with it at a bar. Hell it probably made it worse it was a Black man asking her the same question as her "non-racist" work colleague Stéphane.
And people don't use "Cameroonian-French", unless they're technically binational, which sometimes is the case, sometimes not. They would say "French of cameroonian descent", but there's ways to ask the question and get to that answer. You def don't ask "Where are your parents from", that's synonymous in France with "You're Black so you can't be French". Among black people here we know how to navigate those issues and will loosen up around them but breh came through without that common cultural/social/historical background because he didn't know what was up and his ignorance backfired.