Athlete makes the question a little subjective ...I will say Lance Armstrong just from a pure athletic standpoint...If I had to choose a sports figure it would be Wayne Gretzky ...But damn , I just realized you said American born.
I'm sure guys like Bird, Montana and Clemens will be mentioned.
Elway, in addition to NFL HOF, was drafted by the Yankees, is a great golfer, and is apparently unbeatable in ping pong. But I'm tired of his radio spots pitching used cars... "Who are you going to call, John Elway?" "I'm calling Desert!" Get a tooth tuck you shill