Could the USN blockace the Malacca Straits in a way that only stops ships headed to China while allowing other ships to pass, perhaps with a convoy system?
This is a very lazy question for which you should do your own research on trade throughput, volumes, etc. The least you can do is quantify the parameters involved.
However, in the interests of getting you to think a little, take a look at a map of the countries located around said strait. What do you see? Land, of course. Overland routes to China from Thailand, and Malaysia, and Indonesia, and Vietnam and so forth. Road and rail links which continue to be built out and expanded as regional integration continues year after year. Even if you can magically identify and destroy every single ship heading to China, what exactly stops them from unloading at Hai Phong, the second-largest port in Vietnam? It's only 200km from there to the Chinese border. Is the Vietnamese government going to cut off all trade with China? Is the US going to occupy Vietnam and patrol the border?
And what trade are you trying to stop anyway? What is China importing? Well, mostly commodities. Grain, ore, oil, those sort of things. The kind of things that Vietnam also needs, that everyone also needs. Even if nobody does anything to stop you, how exactly do you track every shipment to ensure that this particular boatload of wheat is being consumed in Hanoi instead of Hangzhou? Or maybe the wheat truly is consumed in Hanoi, because Hanoi already sold all of its rice to Hangzhou and is simply backfilling its own needs. Is that off-limits too? If so, how do you track it? The paperwork alone is a nightmare.
