Regardless of how the economy is going and how many problems we have, the US still has a much stronger political framework than China does. This is because the US is a democracy that allows its people to have a voice in government. This can act as a safety valve, allowing popular anger to drain away to some extent, instead of building up until the whole system blows up. This is why a liberal democracy will tend to be stronger than a communist or other authoritarian structure.
We can see this in the tremendous lengths the Chinese government goes to to make sure that their people will not rise up against them. This has involved things such as blocking texts with the word "jasmine" in them for fear of people planning a "Jasmine Revolution" like the one in Tunisia. It has included the government banning a popular "American Idol"-type show because it was afraid of letting the people vote on anything, even something as minor as that.
Things like that show that the Chinese government is terrified that its people will rebel. We know that the US government has no such fears. This is because the US political structure is much more stable.