American companies, corporations and investors have vested interest in China, more so Internationalist like the World Banks. China is doing this more to have a barganing chip to bring to the table in the future.
Yet the question still stands? Why do we need China, sure we can make our own but think of all the profits that will be lost... bottom line is, the less an electronic device cost, the less profit there is to make...
What you actually have when a product is finished in another country is the ability to skim of the top by every process the product goes through... Its rule #1 regarding money laundring. Also the reason being to control supply and demand to raise prices on an already Recession driven country... think about it... anyways its a theory but one many companies have been caught doing overseas.