>>149301939
That's because to American pop culture, the teenagers focused on were on the older end and played by adults in movies. The whole zeitgeist for teen culture stuff like Teen Titans and Spider-man come from was teens around 16-19(even Spider-man wasn't necessarily a 15 year old initially,that was a retcon). Basically adults without the same responsibilities.
Japanese teens in fiction are generally around 13-15 to start and still not developed entirely yet.