Not quite, while Japan, occupied Korea, and Taiwan provide staging areas for the empire, they don't really have much in a way of their own resources. we already see how the US is struggling with logistics against Iran, and this would be even worse for them. Russia, on the other hand, is huge, has lots of industry, and plenty of natural resources of its own. As long as Russia continues to be aligned towards China, it makes it impossible to meaningfully blockade China. And if Russia got dismembered, then the west would start plundering those resources and cut China off.