You know how the country with the most English speakers is actually China? They got there by bringing in tons of English speakers with few other qualifications besides “speaking English” and making them teachers, because the best way to teach kids a language is to put them in a situation where their only option is to speak it. It doesn’t have to be 24/7, but it does have to be fully immersive and regularly reinforced - they do the same thing in a dozen other countries, and it works pretty well.

In America we have the privilege of not needing to do that in order to interact with world trade, so language learning is treated as strictly optional and not taken very seriously when it’s offered at all. I remember taking Japanese in high school - despite the fact that I lived in Japan I really didn’t learn much at all. Even during class we were still speaking almost exclusively English, so the only people who learned a meaningful amount of Japanese were the people who actively sought out immersion (usually in the form of in-person chat groups with Japanese people who were themselves learning English).