Indeed. The Chinese need US more than we need them.
The fortunes of China changed radically when they took control of Hong Kong. The British Colony had a developed and viable industrial infrastructure. It was this that started the industrialization of China.
But China is low-tech. They get assembly work from many nations, but can't create anything. Surrounding them are high tech nations.. China will take a century to develop the technical abilities of Taiwan or Japan. So China would like to take by force what it cannot create.
The easiest place to do this is Seoul. Using thier proxy army of North Korea, invade the South and snag Samsung, Goldstar, Hyundai, Kia, and other giants. The world knows Obama is stupid and weak - so China might figure they can shove the fiction of unilateral action by North Korea down the throat of the USA; maybe Obama will blame it on an Internet video, or Kerry will blame the Jews. But the administration will not act to protect our ally and risk angering China. This would be the most likely move by China, IMO.