It would take a matter of days until they had massive internal protests. Hungry people topple governments in hours.
I think you misunderstand deeply the current equilibrium in the world.
Most of Africa, a significant part of South East Asia, some countries in Eastern Europe would definitely align with China. A significant part of South America would be neutral.
The USA is losing allies nearly as fast as China is making them.
Yet, it is EXACTLY what Xi repeatedly said in his new-term-inauguration speech
The dictator of China has effectively declared, as publicly as possible, and very specifically, that he intends to invade Taiwan if it does not willingly abandon it's democracy and come under China's rule
He obviously thinks he can get away with doing so without consequences, including those you suggest.
Yet, leaders make such mistakes all the time. Putin just made one on 24-Feb-2022.
It is up to the western world to ensure that Xi sees that such an action would result in bad consequences for him, and deter him from his stated course.
But the fact that it is bonkers is no assurance whatsoever that it won't happen.
That gives us good reason to hope that China will keep behaving that way. We can keep up the deterrence, China can keep on blustering, and nothing bad actually happens. That would indeed be a great result.
Indeed, seems like a most likely scenario.
China can get much further than Russia can in that amount of time.