That's obviously not correct. I can assume just as well that he wasn't poor, reasonably well educated and can speak English decently just based on the fact that he was an American. I can assume that purely due to his nationality because most people sharing the same trait will fit into that bucket. Will I be correct for sure? No. But it's a *reasonable* assumption in contrast to assuming that he was a beginner.
"Assume", "assume", "assumption", "assuming"!
As I said, you know nothing whatsoever about this man or his bike experience, everything you wrote there about him is nothing but speculation. Q.E.D.