I would NOT do it....from my experience it's a dumb series. USASA stands for United States Snowboard Association so it's not really meant for skiers in the first place. I did it at Tyrol 3 or 4 years ago and it's really expensive. You have to pay for the membership (every year), and then also have to pay to enter every competition. Even if you get 1st place you don't even make the money back from entering the competition (ie: $25 entrance fee, top prize $15). Sometimes we won old spring jam shirts or stickers or something too.
I did have fun doing it, because I like competing, but I wouldn't advise doing it just because it's expensive and you don't really get anything out of it.