there's a difference between ussa and usasa
USASA is going to be less intense way more young competitors, more mellow courses, aka a better place to try it out for the first time. There's a good chance you'll be the only one in your age class, but it's good to try out a real course
http://usasa.org/regions.html
USSA races are going to be part of the Rev tour, which will be a lot more intense and serious than USASA, but not quite on the NorAm level