I grew up in south Louisiana and while my grandfather on my dads side was fluent in French (Cajun) and that whole side of the family speaks it; my dad was never taught and I only took classes in k-12 so I can get by if I need to but am by no means conversational! It has made for some funny/awkward encounters at funerals when we see our small-town relatives who still mostly speak Cajun French.
There’s some kind of interesting research about the disappearance of the Cajun French language as a dialect in Louisiana - basically it was treated as illegitimate, instructors were required to teach in English, and if French was taught it was Parisian French. They actually instituted corporal punishment for children who insisted on speaking it in a school setting - and when those kids grew up, they didn’t teach their own kids French.
All this to say, my French is atrocious and my grandfather used to cuss in (Cajun) French because he knew he could get away with it in front of us, lol.