That's because its harder to bribe people in China compared to the USA. There you need to do a shady deal and pay a ton of money, so family gets the inside track.
In the USA, all it takes is a 100K at election time, and its completely legal.
I can't imagine that it's harder to bribe people in China than in the USA. In fact, I think much, much more bribery per capita happens in China than in the US. The Chinese legal system is very weak.
Still, the U.S. political system allows for such an outlier as Obama[1] to get on the top. It would've been impossible if it was only the issue of getting the most lobbyist beef behind.
[1] Not idealising him here, but his ascent was both extremely untypical and very American at the same time.
In the USA, all it takes is a 100K at election time, and its completely legal.