For all its might, remember that a lot of China's soldiers are underpaid conscripts who probably don't want to be there. And in order for it to flex its superpower muscles, it must first pacify its neck of the woods. It'll have to fight the regional powerhouses of South Korea and Japan (one of whom has the second largest navy in the world), with the not exactly weak Taiwan likely joining in.
Then there's also India, dear god, India. Delhi will not tolerate Beijing's ascendancy. South East Asia is probably getting worried and their power is nothing to sneeze at either.
China is surrounded by people who would spend blood and treasure to stop it rising, and if it came to that, opportunistic Russia will take the opportunity to snuff out what could be a real problem.
And to top it all off, there are various ethnic groups in China who will jump at the chance to breakaway when the PLA is off fighting. China has so very many more problems than the West, which will materialise down the line.