This is my understanding of the leagues. The USYSA, by direction from USSF, started creating a system to develop players for the US National team. The latest incarnation of that is the DA.

One (of several) problem with DA was that MLS clubs saw little purpose in developing players for the National team. LA Galaxy, for example, was much more interested in developing players for the their own team.

Meanwhile, state organizations, each separate but under guidance of USYSA created their pathways and rules to support the vision of USSF. Some did better, some worse. Several clubs though were unhappy. This allowed a private entity, US Club Soccer, to fill that void and create competitive atmospheres that meet the needs of the their member clubs.

On the boys side, the parallel to DA is the ENPL. The NPL s more regionalized, closer to the intent of the Piedmont League (which is a step below the National league). To compare:
https://www.nationalpremierleagues.com/npl-leagues
https://www.usyouthsoccer.org/piedmont-conference/

SCCL and even moreso, CPL, have no fair comparisons. These leagues were organized by their member clubs under the US Club Soccer umbrella, and out of the State leagues (for the most part). Each club has their own reason for entering into this relationship. The CPL (Carolina Premier League) is one of just nine such leagues nationwide (source: https://www.usclubsoccer.org/premier-leagues

scsoccerfan123D has a point when he says it is a somewhat of a phenomenon here. As for its quality relative to the non-CPL teams, that is debatable. The SCCL and CPL have each clubs strongest AND weakest teams. Most of the biggest clubs in the state are members. The glaring exception in the CPL in the Low Country is CBSC, which won 70% of its matches against CPL clubs at the MB tournament in April and had 41 teams across all age groups. Although they applied to enter the CPL, they were denied with no reason given (the CPL does not have a defined entrance criteria. Its members vote on entrance, and it must be unanimous).

Hope this helps