Er, I don't know what's happening, but since updating, my iTunes store is now in French.
It appears to be the actual French store. I have access to the European version of an album I couldn't see before -- and it even includes French versions of the songs. (The album is "Steady Pull" by Jonatha Brooke.) I have options like "Voir tous les albums," "Me prevenir," and "Recommander." If I wish, I can "acheter l'album" for 11,99 euros.
I'm reasonably sure it's the French store, and not simply IN French. The top album is currently "L'eau" by Jeanne Cherhal. Maybe I'm getting really old, but I don't think that's likely for the US, since I've never heard of Jeanne Cherhal.
Has anybody else experienced this? I've restarted the app several times. iTunes itself is still in English. Only the iTunes Store is confused. How do I fix this?!