How do you come to the conclusion about their ability to protect those areas? What do you believe it will take to knock out that dam?
Well, you put the shoe on the other foot.
What evidence can you provide that China has the capability pf protecting the Pearl River heartland? of Shanghai? of vital ports?
There are several videos discussing the vulnerability of the dam. Apparently The means exist. The current news is that Chinese air defense systems failed to engage the recent successful air attacks on Venezuela.