Sometimes it’s nuanced. Sometimes it’s blatant. Mostly it’s hilarious. Americans have taken some French words or sayings and made them something they aren’t to the French. If you know of any not on this list, please leave a comment, and I’ll add it!
Ooh la la!
To Americans, this phrase means “Well, isn’t that fancy.” It’s a response to a friend showing off a new designer purse, for example. When the French say it, there are usually more “las.” It sounds like “ooh la la la la la la!” It doesn’t mean they’re impressed. It means something like “What a mess. How annoying.” It’s a common response when a child drops something and it breaks all over the floor, or when a child falls and starts screeching.
This one has a hilarious backstory. My boyfriend’s mother asked him to hand her a casserole from the kitchen cabinet. I stared at them both. “Don’t you refrigerate your casseroles? The French make shelf-stable casseroles?!” They stared at me, and he got a “casserole” out of the cabinet. It was a cooking pot. It wasn’t even the flat, rectangular baking dish that Americans bake casseroles in.
To Americans, this word has a romantic or sexual connotation. So when I heard a French person say they had a rendezvous with their hair dresser, I was curious. “You’re sleeping with your hair dresser?” That’s when I was told that in French, it just means any kind of meeting or appointment. Not necessarily sexual. Probably not sexual, in fact.
A la mode
In America, this phrase means “with ice cream.” In French, it isn’t used to mean anything other than its literal meaning, “in the fashion.” If you ask a French person to serve your dessert “a la mode” they’ll just give you a funny look. “In the fashion of what?” they might ask you.
Apparently, this is a name in America. In French, it means “the watch” (la montre). The most common reaction I’ve heard from French people upon learning that this is used as a name in America is “Really? But why?”