They're dependent on western economies to _buy_ the stuff they make (more on that later, re: political stability being tied to their exports). They're dependent on some western countries for natural resources and raw materials. If shit hits the fan, you want to be the producer not the consumer.

Take a look at this: [atlas.media.mit.edu]

You'll see that the biggest chunks of their trade exports are relatively-high-tech products (much to do with computing and telecommunications). Their technological level exceeds what you'd expect of a country with such a low GDP per capita.

For reference, I think many people will not doubt that Russia is a country which has much more "actual power" than its economic statistics indicate. This is not only due to its nuclear weapons, but also due to its strong technological standing in particular industries (e.g.: space, rocketry, military vehicles and planes and weapons). China is a bit like that, to a lesser degree. It makes cheap crappy stuff, but it is also capable of making things which put it in an exclusive club of powerful high-tech countries.

I'm a subscriber to the Association of Computing Machinery's newsletter, and every week there will be headlines about new computing developments researched in China. If you include research done by the hordes of Chinese PhDs/postdocs in overseas universities, it gets more extreme. They're making huge strides in the information technology front, and this is the Information Age. To see how IT crosses sectoral borders into other areas, here are examples: (http://www.popularmechanics.com/military/research/a24494/chinese-drones-swarms/), (http://www.itv.com/news/2017-06-23/how-chinas-facial-recognition-technology-is-changing-daily-life/).

What do they have?

(1) Hell of a lot of people, who are reasonably educated, and very hardworking.
(2) Crappy political governance and institutions: their elites are often extractive and exploit people and then ship their money out to the US or other western countries.
(3) Middling technology in most areas, but high technology in some (IT, telecoms, rocketry, infrastructure).
(4) A massive manufacturing base, covering large swathes of the global supply chain. Global trade of manufactured products would grind to a halt if Chinese factories disappeared overnight. Much of this is concentrated in low-tech crappy stuff, but there exists a significant presence in crucial links in the supply chain which are not easily replaced.
(5) Disproportionately (compared to GDP/capita) strong education system and infrastructure.
(6) Strong political unity amongst its people, who are willing to put aside their differences for continued economic development for now.
(7) Severe environmental degradation in parts of the country. Note that many industrialized countries went through this phase as well, including the USA, Japan, UK.

They also have very severe weaknesses:

(a) Political system still under development, and subject to big changes as they move through the developmental ladder. It's not inconceivable for their progress to be wiped out by a political revolution. The thing is, the people are aware of this, and I think most people know that their government (CCP) is often corrupt and quite bad in many ways, but they put up with it in the name of continued development. If the growth continues, the politics remain stable. But the growth may not continue, as China approaches middle or mid-high income levels. Then the government needs to fix issues like corruption, environmental degradation.

The current President Xi Jinping is making material steps towards this. It could potentially all be ruined if he picks a bad successor and fails to exert his influence from behind the scenes after he steps down. I think of Xi as somewhat similar to Putin: canny politicians and authoritarian leaders who are acting in their countries' best interests. Interesting note: he has quite fond personal feelings towards the US and its people, check out the wikileaks cable sent by US intelligence on Xi Jinping (https://wikileaks.org/plusd/cables/09BEIJING3128_a.html). If you read this you will know why the CCP has picked the correct guy to lead it for now.

(b) They need to import massive amounts of energy and raw materials through sea lanes presently guaranteed by US security. China has benefited greatly from the US system of maritime world trade and security guarantees. The nuclear umbrella covering Japan preventing potential militarization in Japan is one example. But they're fearful that the US will get jealous of a rising challenger, so they want to secure the South China Sea trade routes themselves, with their own domestic navy. Hence first they must secure Taiwan as the "unsinkable aircraft carrier", and they must get the first island chain secured. Additionally, they are doing One Belt One Road to boost overland trade in the Eurasian continental bloc.

(c) Demographics. Population is too large for its natural resources / size of usable land at present. This trend is being reversed largely due to the One Child policy. Now the One Child policy has been slowly rolled-back: most new couples nowadays can have two. Ageing population: this is a huge issue. It could wind up like Japan if it cannot make enough young people (or successfully integrate young immigrants, which I strongly doubt).

Greatest threats to Chinese development:

(1) Political corruption / betrayal by elites.

(2) Demographics (ageing population being a burden on the working young).

(3) Taiwanese independence or some other severe challenge to their control over the sea lanes they depend on.

(4) Disaffection against a non-representative elite-rule government with significant corruption leading to social instability. This is less likely to happen if they fix the corruption problem. I guess you could do psych-ops to influence people to hate their government, but that's precisely why their internet tech is isolated from the global US-mediated internet tech. Google/Facebook can strongly swing politics, but most Chinese can't/don't use Google/Facebook.