I think you make a good point, but I'm not sure that the perceived benefits to China of tying up American resources outweigh the downside of having a massive American military force only 350km from the Chinese border. They would much prefer that the problem go away. Similarly, while Afghanistan and Iraq have weakened American militarily, they've also radicalised loads of people with very close links to people in Western China. So ultimately, while Afghanistan and Iraq have been bad for America, they've been bad for China too. There seems to be a conviction in the US that China is seeking military superiority over the US. If it were, well, for starters it would be spending more than 20% of what the US spends on its military. China can afford to spend more (unlike America), but it chooses not to. And China wouldn't be putting so much effort into propping up America's economy. China has enough problems at home: it doesn't need military confrontation overseas. And, as JMD says, China is so reliant on global trade that it can't afford the economic disaster that a big war with America or Japan would bring. To the degree that China wants global power, it would much rather buy it than fight for it.
China will continue to give NK enough food aid to stem the flow of refugees from NK to China, and no more. The current Chinese administration would never give NK military assistance: they hate the North Koreans at least as much as the Americans do. Indeed. But that's in no-one's interest, and it's not going to happen. I don't think China's nervous about America's actions. They're nervous about the North Koreans, but the only thing that worries them about current American actions (such as the stealth bomber flights last week) is that they might spook the North Koreans into doing something really dangerous.
The USA, Japan, Taiwan and SK military is under served compared to China, NK and Russia. China's navy is over a 1,000 ships compared to the USA 20.
While we tend to keep these as distinct paths, I won't be surprised if they turn out better than us, or at least fairly good, at balancing and integrating these approaches to the same strategic goal.
That appears to just be what the US has in the region, with more being sent. And what defines a ship on that graph? Does China's thousand include river patrol boats?
I recently got back for 18 days in Central America. China is investing and buying influence in the area. I suspect their methods of doing business and donating large projects will in the long run leave people there with a favorable impression of China.
China has the local advantage of never having backed the overthrow of a Central American government or having supported a repressive dictatorship in Central America. China isn't nearly ahead there yet, but they are making progress.
While some say NK is a drain on the US, I think the Chinese would prefer a smaller American presence in Asia. Their best-case scenario is NK scales down the rhetoric and fix their economy. The fall of NK would be a big mess for the Chinese - refugees, possible fallout, etc. I hope the Chinese are considering closing their border with NK long enough they come to their senses.
Perhaps we need a cultural exchange program. We can send the Victoria Secret show to them. That should help.
^ The average NK person probably can afford only that much clothing (less headdress and jewelry), albeit not as sexy....
Cnbc says the SK stock market is not even impacted. Evidently that are a nation if bluffers, and they are hoping the world lifts the embargo. This is just what they do. In a few months it will pass.