The same "so what" as Vietnam, and the same "so what" as Japan circa WW2: the US does not want to see a pan-Asian superpower, either officially (see: annexation

The same "so what" as Vietnam, and the same "so what" as Japan circa WW2: the US does not want to see a pan-Asian superpower, either officially (see: annexation of territories by Japan in WW2) or unofficially (see: Soviet vassal stating of Vietnam). As a superpower the US's interests are necessarily long-term, strategically. Sure, the immediate reaction of China jack-booting all up and down the Pacific Rim would be economic and political turmoil. It's the long-term possibility: Chinese hegemony over the entirety of the Pacific coastline, that scares the shit out of the US. Bear in mind that the USSR, despite not being an export power (like, ever) was still able to pose an enormous threat to the existence of the USA. China losing its preferred-manufacturer status wouldn't be consequence free, but it also wouldn't de-claw them.