American tennis has gotten worse, because more money is poured in football and basketball on every level high school,college, professional. There are not as much children in general, who want to go all the way to become a professional tennis player in the US. Actually John Isner and Sam Querry weren't even confident they were going to play pro tennis. John had to 'flip a coin' between basketball and tennis and went to college. Sam Querry wanted to go to college as well. They don't have motivation like European players do, since they have been young.
My college tennis recruiting video. Over 70 000 views! Please tell me what you think. http://www.youtube.com/watch?v=gJUac_sj1sY