For admission into the NPL and CPL you are voted in/chosen by the board/directors/whatever. USAMP votes/choses against other local teams. Such was the case of GPS girls not getting NPL.
Where are you getting this information from? While I am not a board member of the NPL I’m quite confident that USA didn’t prevent James Island from joining NPL. Keep in mind JIYSC falls under the GPS umbrella and GPS Carolina, as you’ve already stated, have a presence with US Club Soccer. GPS Girls not “getting” NPL this past year had zero to do with USA and everything to do with that girls team again being a challenge team.