Well, the islands of St Pierre et Miquelon off the Eastern seaboard of Canada belong to France. They are FRENCH no matter who invades and says otherwise.
Just like the Falklands are BRITISH no matter who invades and says otherwise.
Just like the United States is MEXICAN no matter who - oh wait. Never mind.
I believe during WWII, that was the site of the first victory of the Free French, over the Vichy Government.
If the Mexicans wanted to buy back California I wouldn’t object.