Only when the soviets and others started doing so to did we start trying to “crack down” on them... but the real truth is we were only cracking down on the old ones others were using while constantly staying ahead of the testing curve to continue our fake dominance.
There is nothing in the American DNA which would explain our dominance, or that explains the sudden magical leap black athlete's made in the 20’th century.
Actually, there is something that would explain the sudden magical leap black athletes made in the 20th century. It could be that people whose genes predisposed them to superior athletic ability were finally permitted to compete.