I read an article a few years ago that gave a good analysis of why there are no competitive American heavyweights. The writer linked it to the American passion for record-breaking in other sports. Players in baseball, hockey, etc., are getting bigger in order to run up scores, break records, etc. So, any kid who's big and shows athletic ability doesn't go into boxing (where only a small handful of contenders actually make money and get the piss beat out of them) but goes into a team sport. There he can have a lengthy, well-paying career even if he isn't the top player--and live to tell about it. That analysis also hints to me why steroid use is rampant--the bigger the guys, the more records broken.