I'm not the in US, so my knowledge of the educational system comes only from what I read, but it's my understanding that "extracurriculars" are an important part of college admissions, which is different from Europe.
That's really only a thing for the private universities and those don't make up a large percentage
That's not true in my experience. In my state and surrounding states, most of the large state schools care a great deal about extracurriculars.
The person I was replying to was saying how they're 'very important' in Europe though.
In Europe, it's important that kids learn self-development, so we let them do it. And they do it by hanging out with friends, learning an instrument, etc. They're not pushed to do those things because colleges don't take these into account for admissions.
In the US, it's important that kids learn self-development, so we have them learn an instrument, or participate in sports. They are pushed to do those things because colleges take those into account for admissions.