It would probably also explain why there are so many American climbers. We have a ton of mountain ranges (including but not limited to: Cascades, Rockies, Appalachians, Alaska Range), that all have different peaks, difficulties, climates, etc. So it is possible to train yourself on climbing something like Pikes Peak, Rainer, or McKinley before you prepare for "The Big One" as it were. McKinley especially since it is the second highest behind Everest IIRC (and certainly in the top 5 if it isnt).
It would probably also explain why there are so many American climbers. We have a ton of mountain ranges (including but not limited to: Cascades, Rockies, Appalachians, Alaska Range), that all have different peaks, difficulties, climates, etc. So it is possible to train yourself on climbing something like Pikes Peak, Rainer, or McKinley before you prepare for "The Big One" as it were. McKinley especially since it is the second highest behind Everest IIRC (and certainly in the top 5 if it isnt).