The first important fact is that most of the show jumping stud farms are in Europe, which change already a lot of thing. European communities have more experience with young horses and even amateur riders train their young horses.
In the meantime in the US, the horses are mainly imported from Europe so the market is more focus on finding the right horse and rider combination.
As for the competition, the show jumping history started in Europe, so the show program is guided by the european ones (against the clock, grand-prix, …). Our sport base is in Europe but the sport is becoming more and more global. For example, when it comes to international shows, the FEI rules are the one who control all the CSI in the world.