Heres a list of Airports in China vs the US. Looks to me that America has a lot more smaller airports, vs china which mostly has bigger airports for airliners and such.
I can't speak for China, but after a quick glance, I can name two actively used airports in the US that I can find on this map that are nothing more than flat stretches of dirt.
[Edit] They're generally used for hobbyists. Although, I once watched a V-22 Osprey practicing touch-and-goes at [1] below -- kicked up all kinds of desert dust. I've never felt more like being in Half-Life than at that time.
The US is fairly unusual in its vibrant general aviation infrastructure. A lot of those airports are tiny ones suitable to only propeller and small jet planes, not airliners.
China's extensive recent work on a high speed rail network is probably relevant here, too.
Seriously! Russia too. It looks like there are more airports in New Jersey than in China and Russia combined. That's got to be _some_ kind of opportunity?
This is more of a regulatory issue than anything. Airspace is very strictly controlled in both countries.
Further, outside of NA and Europe, GA is simply not as commonplace and in many cases like China/Russia, it's because it's (for all intents) inaccessible. Besides being heavily regulated, it's also relatively expensive, even by first-world standards.
Does anyone know if the data is incomplete for China, or is this accurate?