Oh come on, nearly all the great pianists you can name spent most of their childhood sitting in front of the keyboard, whether they're from China, Poland, or the US. That's just the way it works. Same with violinists, figure skaters, gymnasts, etc. If they're not pretty amazing by the time they're 12, they're probably not going to have a career.
And it's only the US that places such a premium on "being a kid" -- meaning I guess playing video games, hanging out at the mall, and generally misbehaving while the parents are at work. In other countries they get to play all they want for the first five or six years, after that they're expected to buckle down and start doing serious schoolwork, music practicing, etc.
Is our system better? Are Americans happier than people in Europe, Japan, China, etc.? I think you'd have trouble making that case...