Something tells me that it's related to the relative independence that school age kids experience in Japan when outside of school. Long solo commutes on transit are OK even for older grade schoolers. And the pop culture tends to put a lot of emphasis on the school age "best years of our lives" trope - witness the endless number of high school manga settings - because the working age world in Japan still offers comparatively longer hours and less freedom. If you take that thought to its cynical conclusion, that you cease to be a person with any kind of personality or agency after graduation - well, why respect the school system and the class popularity contests?

In the U.S. the helicopter parenting strategy mostly prevails since society has a tendency to call the cops on "negligent" parenting. There's a ton of focus on attendance numbers and graduation rates. Depending on where you are, school can be an academic pressure cooker or a pipeline into the prison system. There are more immigrant communities pushing for "first in the family" success stories. And so the attention of the student gets away from how bad school is and gets diverted towards "surviving the zombie apocalypse/battle royale and riding off into the sunset".

Many people entering adulthood here, at least since the recession and perhaps earlier, experience a crisis a short while after they graduate and enter the workforce because they have been so steadfastly committed to this kinds of script from an early age that they can't reflect properly until much later, and then it hits like a freight train that they might be wrong, their identity is incompletely constructed, and the story did not end with them riding off into the sunset.