And Title IX has dampened prospects for American men who play non-revenue sports.

My theory on US tennis is the demographic that would play it sees better opportunities and enjoyment in other sports. Tennis, like skating and gymnastics demands a level of individual commitment few would care to give. With so many other options, particularly in team sports, it is the rare American athlete, especially the American male, that would concentrate on tennis or skating or gymnastics. The most common individual sport I hear of for American boys is swimming. After that I suppose it is golf but they are a rare breed. And still, swimming and golf have teams that provide a "club" experience. From what I've read about the junior ranks of tennis is the competition is universal and unrelenting and that makes it a very difficult environment.

From Australia:
"Tennis can be a selfish, lonely sport. The urgent race for higher rankings, better pennant teams, individual tournament success, coach hopping, doubles partner swapping and more choices and changes are made with an entirely selfish purpose."

http://blog.scarboroughtennis.com.au/why-the-junior-tennis-culture-needs-to-change/