US training is in terrible shape. All of tennis has turned to modern slow courts, yet in America is all fast hard courts, so guys in the US reach the pinnacle, while their European counterparts get their foundation on clay, so once an American goes pro he has a huge learning curve to adapt to slow courts including US Open, they know this but do nothing about it.
Also, those of you who vote for liberals, big Government, are you surprised that you need a LICENSE to teach tennis?
Third, players learn with large racquets and baseline play, the reason is that naïve parents want results, so if the coach did the right thing, started them on small racquets to get their fundamentals down it would take longer, but they'd be better players. It's easy to teach a kid with a huge racquet to hit from the baseline, the parents think "Oh look he's learning", coach gets paid.
Lastly it's our "Everyone is a winner, everyone gets a trophy" entitlement society, it's ruined kids. When I was a kid I trained like a maniac, ran 5 miles then played tennis because I wanted to WIN, there is no hunger, America has turned into a sissy society where we expect everything handed to us on a silver platter.