Where do their raw materials come from?
China does indeed have a monopoly on precursors.
https://globalnews.ca/news/6570411/covid-19-drug-shortage-worry-canada/
Precursors are simply a recipe of raw materials, the world supply of which China does not control. China manufactures these items because it was an easy task to pass off. Watch how fast we bake the cake if we need to.
Everything China does, can be replicated. Down to rare earth metals - which we have an abundance of. Mr BP works all over the US on very specialized manufacturing equipment. America can produce anything, anywhere, given some lead time. Think WW2 production levels ramped up again. Rising to challenges is in our blood.