US focuses on hard courts. That is a big factor. You must be fit and commit to defense to win on clay — something American players do not do that Europeans excel at. And since all courts play similar (slower than 20 years ago) and all players play from the baseline, you better have a rock solid backhand and be able to cover a lot of ground.

I thought we had a couple real top 20 prospects in Tommy Paul and Reilly Opelka, but I haven't seen enough progress. There have probably been 40 different US women in the top 20 in the last three years, but none look like they are ready to win a slam right now. Sadly, Sloane has dropped off. She was the real deal when she won the US Open. If Serena doesn't win Wimbledon, I think she is done.