I don't get the food problem in a blockade? Wouldn't Russia, Central Asia, and continental ASEAN provide the food via land in such a blockade?
This assumes China doesn't produce enough food for herself (a questionable assumption).
The United States could try to bomb the trading routes. But China's land borders with Russia, Central Asia, and continental ASEAN are 15,000+ kilometers long. You're talking about continuous multi-thousand kilometer stealth bombing runs to prevent 15K+ kilometers of potential border trade - while at the same time needing to bomb military bases and military production. It sounds like a great way to attrit B-21's.
Finally, the War in Ukraine shows that civilian infrastructure is difficult to destroy. Both sides have found it challenging to destroy simple bridges; Russia hasn't managed to fully turn of the electricity in Ukraine after months.