The lower tiers of North American soccer are rebranding by way of English football.
The USL is undergoing a number of changes, with the addition of its third-division league in 2019, and it's altering how all of the leagues below MLS will be called. What is now the second-division USL will be known as The USL Championship, the new third-division league will be known as USL League One and the Premier Development League (PDL) will be known as USL League Two.
The structure is not unlike how it is in England, where the EFL's tiers below the Premier League are the Championship, League One and League Two. The major difference, of course, is the existence of promotion and relegation in England, whereas that is not yet prevalent in North America. Leagues and clubs in each division must adhere to the standards set forth by U.S. Soccer under the current system.
The USL, as it currently stands, has 33 teams and a number of more lined up to join the growing league, which is approaching 40 clubs. The third division currently has eight sides lined up for its inaugural season.