It isn't very hypothetical, the United States imposed upon Iraq horrifying sanctions, to the point where pencils were prevented for export at the risk of usage for nuculer purposes. If the United States became any less popular on the world stage, it is certain Taiwan could embargo the US, making the Myanmar floods disrupting industry looking like a pittance of disruption.
I presume you mean china rather than Taiwan, but the short answer is that sanctions are only as good as leverage and the popularity of the people imposing them. Getting sanctioned by the US is a big problem, because so many other countries will cut you off rather than jeopardize their own trade relations. Getting sanctioned by China or Taiwan would be a genuine problem, but neither country has so much leverage that they could get everyone else to go along.
The US is at a historical nadir of popularity, perhaps for structural reasons. But even if it were wholly isolated, its internal resources and expertise are more than sufficient to operate as an autarky.