Question About China's Economic Future?

Experts predict that China will overtake the U.S. economy in as little as two years from now. I don't want to be rude to the Chinese at all, and I am happy for their success, but I have a question. Up until this point, China is only rich basically because America is rich? Correct? I mean their boom happened when America started building factories in China. So I have a question. Is China being the biggest economy really even that valid? I am saying would it really truly be the largest economy if, in short, the economy is basically America's, since we are the one's buying everything from them? When America was starting, it used to be supported by Europe, but then it broke away and created an economy within it's own country, that is why we have been growing so much for two hundred years. Will China do the same thing and break away from America and no longer be dependent us buying. What I am asking is that even so in all technicality, China is destined to be the largest economy in the world, does it really mean anything since America was and still is it's complete reason for it's it's success? If the American economy crashed tomorrow I would presume China's would too. I would also like to add this isn't some sort of a hate thread or anything, and it's not that huge of a deal, since second is still good, and America can't stay number one forever.