@Chinese-Dragon has already explained it pretty well in his post. I will supplement his point with a bit data. The following link is a detailed break down of US-China trade by category of goods: (you can play around with it to see different partners and the trade volume, it is a very useful site)
Trade Map - Trade statistics for international business development
Total Chinese export to US in 2013 is 369,111,212 USD, total Chinese export to the world is 2,210,522,658 USD. Basically, US' import from China accounts for 16.698% of the total Chinese export.
In comparison, Chinese import from US in 2013 is 153,606,906 USD. Total US export to the world is 1,949,934,687 USD. So China also accounts for 7.878% of US export, but wait, since the theoretical trade barrier is erected on US side and it is supposedly able to complete cut off US-China trade, then even though China's 16.698% will be affected, the entirety of US' import/export would be affect because a barrier of such magnitude will most certainly affect US trade with other country as well.
I am getting off topic. The bilateral trade discussion is nice, but it is not related to the original point. The original point is regarding to US investment. The Chinese economy's dependence on US investment is quite small, largely because US isn't a major investor in China to begin with..
You compare China export to the US vs the world? How many continent and how many countries are part of this world? What are the total population in this world excluse China and US population? What the percentage of the world population live in the 3rd world and developing nations? What amount GDP and PPP of US, E.U, and Japan combine? Can China turn against the West and make them China enemy without hurting China economy or slashing 2/3 of China annaul GDP rise?
You get the better understand with US and the West still hold the economic cloud over the world after you answer those question that I posted.