>>518853909
Any country cutoff from trade partners will suffer a contraction and depending how severe it can destroy the country or just cause a bump in the road. It isnt simply losing customers but losing suppliers.
China lacks in advanced metallurgy, gas turbines and a few other industries and of course they need food imports. If they get cutoff, they would have to adjust by replacing them or settling at a lower level of technology. Overall it seems like a modest challenge for China.
Their push for electric cars is an attempt at not being overly dependent on oil imports. Without trade, they would have to eat less meat as there would not be so-y imports, they would have to use more steam turbines rather than gas, and at a lower temperatures if they lose access to alloys, less electricity and industry overall. Not pretty but China used to be 10 times poorer so a 20% drop isnt going to kill them.