Professional soccer is international, and tying sports to school is a uniquely American thing. In professional soccer, clubs run youth academies and teams. The best players graduate to higher level teams within the clubs. The best of the best will ultimately make it to the "first team", and that could happen at any age.
The American system of tying sports to school is dying because collegiate, and to some extent high-school sports, has lost it's amateur status at the highest level of competition. They're players first now, not students. Any illusion of that not being the case was destroyed by NIL.
When there were fewer professional opportunities for American soccer players the number going to college to play was actually pretty high. Even 20 years ago, USA legends like Clint Dempsey were playing 4 years of college ball. Today we have kids performing well in their academy teams, playing a year or two in MLS and then getting shipped off to the biggest soccer leagues in Europe.