It's also entirely possible that, on average, Asian people are more intelligent than other groups. We won't really know for a long time, as discussing such things is taboo.
Scientific discovery and technological innovation takes more than hard work, it takes the willingness to be obsessed with specific and sometimes obscure fields and forfeit social prestige and stability. Neither of those things are praised by the Asian culture.
I would say it's very possible that genetically, the Asian population in America is smarter than the average American. Combine that with a culture that emphasizes hard work and education and you'll have extraordinary results. But don't think that Asians are more intelligent as a whole. There are plenty of idiots back in China to balance that out.