American white men are mostly soft, effeminate, overweight guys who watch too much TV, drink too much beer and eat too much junk food. Such men are not cut out for boxing.

The only good one I can think of in recent years was Kelly Pavlik, but he ruined himself with alcohol.

But there have been plenty of good white boxers from other countries such as the Klitschkos, Dariusz, Calzaghe, Povetkin, and many more coming up now such as Ponomarev, Gvozdyk, Beterbiev, Usyk, Lomachenko, Derevyanchenko, Magomedov, Mekhontsev, etc.