spot on
training only gets you so far (soon the kid will realize you will always look pretty in training).
next will be match experience and then the rude awakening that you will loose, you will fail, and then how to get back up.
winning as a U13 is always so much easier, the challenge isn't at U15, but rather U17/U19 when the distance gets pulled apart - separating junior levels to the senior levels.
Then it will come to fatigue, and doing the same thing every week for the next few years. It will get bored,
The physical, psychological and strategical aspect of the game has yet to come and some kids will just struggle with 1 or 2 or all 3 aspect of the game. I guess kid being in USA will have 10 times less pressure than the kids in Asia, so a bit less harsh on the psychological side of things.