I disagree. AAU(or summer ball) gives kids a chance to compete at a level not available locally. In my experience, there are some summer coaches that simply say run and press. There are some very good coaches also. Also, most kids work on fundamentals with their high school coaches in the summer and use the summer tournaments to apply what they have learned. I have seen first hand, kids that have bigger improvements in each summer than during the high school season.
I do agree that a good percentage of NBA players will be from Europe, but not because US ball is getting worse but because European bball is getting better.