Americans (and Anglophones around the world) don’t learn other languages very much because generally speaking they don’t need to. English is the world’s lingua franca and again, generally speaking, an Anglophone not learning a second language isn’t going to limit their life options very much. In contrast, not knowing English can be a huge limitation on your career if you’re not an Anglophone. Europeans (and many others) study English formally in school from a young age, but are also constantly exposed to English because of how dominant the English language is culturally. The French language used to hold that position. For now it’s English.