Simply put, without liberty, China will strangle itself economically, culturally, and politically. The most important feature of progress in free makets is failure. Failure does not happen in China.
That is not to say America is not in decline, or that China, like the old Soviet Union, cannot cause great distress to free countries for a nickel on the dollar.
Ironically, if China were to succeeed, it would only be through increased liberty, and that is a good thing for everybody.