If you no longer have foreign contracts (US) to keep your plants in production, you can no longer provide jobs for your state employees.
If you can not provide jobs for your state workers, they can no longer purchase food to feed their families.
Without their primary income coming from the US, they can not purchase the necessary fuels to run their energy needs or fuel their economy.
China is the largest importer of oil in the world, shut down their ability to purchase and their suppliers and China is dead in the water on all fronts.
Comrade you have never lived in a Communist country. Too keep people "busy" they build entire empty cities in China.
If you can not provide jobs for your state workers, they can no longer purchase food to feed their families.
Work can cease to be voluntary Comrade.
Without their primary income coming from the US, they can not purchase the necessary fuels to run their energy needs or fuel their economy.
Gulags don't have much in the way of heat.
China is the largest importer of oil in the world, shut down their ability to purchase and their suppliers and China is dead in the water on all fronts.
Cars? they'll go back to ox carts and bicycles.