The only point to ICs in Sinkiang/China is if you have one in India and you are leaning hard on Japan.
You can easily build fleet and force the Japans into countering you instead of attacking SE Asia while you secure your territories and get your factories running. Then retreat the fleet or press the advantage depending on your own style. After all, once you have a significant force in SE Asia, there’s nothing Japan can really do to get out of it.
Actually, if faced with this as Japan, I’d recommend leaving FIRST. See if you can blockade England and relieve some pressure on Germany. It’ll take a few rounds for America to get your islands and while doing that, they’re not invading Europe.