Culture is huge. Japanese kids want to be fast. American kids want to be football stars. American girls just do the sport to be skinny.
My friend coaches at a high school that is often one of the top 3 California schools at state, all divisions. He says the girl's team, who wins, pretend to go for morning runs but just go sit in their cars, only running at afternoon practice. The 1st and 2nd girl on the team actually do their morning runs. The 1st and 2nd girl both go top 3 at state. The rest are back from 15th onward.
The other girls are afraid to run too much because they think they will get stress fractures from running 20 minutes easy, 3 mornings a week. That is America.
Meanwhile the Japanese don't question it and do what their coach says.
Also, as mentioned, Japanese high schoolers are recruited. A high school with 5 14:08 guys didn't pick from the pool of the 500 closest boys.