Personally, I think it's kind of a weird balance.
I feel it's best to look at other sports. If you look at basketball, America's dominance has come from the inner city and pick up ball, not working on strokes, footwork, etc. But on the other hand, you need hours and hours of working on your shot (elbow in, rotation, free throws).
Soccer? Way too structured and we suck (compare to Brazil, etc.).
Baseball? Falling behind to small islands like the Dominican Republic, where they play ball in the "streets."
We don't see that in tennis, it's actually a lot closer to soccer then basketball.