USSF (club) is very hierarchical, from local teams right up to international competitions. MLS has their own referee organization called PRO, but they use USSF referees to start with.

NHFS (high school) and NISOA aren't very hierarchical. They should really just adopt fifa rules and hire USSF referees, but they're driven more by politics and state governments and tend to be slower to adopt rule changes.

High School, it's up to who the state assigner thinks is good and which games they can handle, except most states have minimum seniority requirements for doing playoff games.

For college games, each conference has an assignor and referees tend to start in a smaller lower division conference, and then get the attention of bigger conferences like the Big12. They also pay more. So in that sense, there is advancement, but you can get situations like travel costs and such which influence who gets which games. The college playoffs are very competitive to referee.

Many referees are certified for USSF, plus one or both of HS/College associations. When I lived in Cedar City, I'd do all three. Refereed some BYU vs. SUU games, but the men were USSF because it was club, while the women were NISOA. Ended up eventually not recertifying for college because the smaller conferences don't really have money for travel and accommodations and there's are thus only a couple teams to do in Southern Utah. It's not like you can do all the same teams' games, so it wasn't worth the expense (referees buy their own uniforms and equipment).

I still keep up with the rule changes, though. 🙂