Because having only the United States as a super power has limited individual states' agency to follow their own course. The US does everything in it's power to force countries to open up their markets and resources to large multinational corporations. This often results in the poorest folks on earth having their country's natural resources robbed from beneath them. Having another large power means more economic systems can take hold.
As for things domestically in China, international groups have found overwhelming satisfaction and support for the government there.