Nope. The US couldn't save South Vietnam, Iraq, Afghanistan, Ukraine, etc.
Ultimately it's up to the nations of the South China Sea to defend themselves and each other.
China's greatest weakness is its need to import food to feed its population. Granted, the Chinese Communist Party does not care how many of its citizens would starve if a blockade was to stop food imports. The Chinese Communist party is willing to incur millons of casualties to achieve its goal of re-unification with Taiwan.
Much like Japan in the 1930s, the Chinese Communist Party will need to conquer, occupy, or exert influence over resource-rich nations on which it relies for imports.
When looking at the Chi-coms' imperial ambitions, it's important to include former protectorates and tributary states. A map of the Q'ing Dynstasy's reach and influence as of 1820, is a starting point for understanding what the Chi-coms' ultimate imperial ambitions may include:
Xi wants to restore China to the power and prestige it once had prior to European interference.
The greatest regional check to Chi-com imperial ambitions is India.
