USA Softball - has died in many places and at most levels. The Super is a collection of All Star teams that don't play together all year. Same with AA. Fewer and fewer teams at the B, C, D, E levels for worlds.
NSA - Disappeared for most of the country
One World (or whatever it is) is regional.
In Seniors, you have ISSA and SSUSA as the largest two. USSSA has not caught up to either one, and probably will not with their rule changes (nets, etc.), which are geared toward safety, but not what most of the players want.
USSSA is still the best for Non-Senior level of play, especially at the National Level.
In California, historically it went from predominantly USSSA, swung to ASA (because of better leadership at the local level with state and local directors). It has now swung back to USSSA with USA/ASA having to cancel most tournaments due to lack of teams. There are some small local associations, but not national, and definitely at lower quality of game. But they serve a purpose and let upper level players mix in with friends to get some games in.