One argument for not worrying about things we need in a crisis — steel and the like — being manufactured abroad is that as long as allied countries are making it, there shouldn’t be a problem. But we’ve seen in this crisis how even allies can be disrupted, and even allies will attempt to keep necessary supplies from one another (something that’s been happening within the E.U.).

A New York Times report notes this dynamic:

Even before this crisis emerged, the Food and Drug Administration noted shortages of well over 100 drugs in the United States. And factory shutdowns in China, India and other countries may have exacerbated the shortage of some ingredients and generic drugs during the pandemic.

“Out of 21 antibiotics that would be critical for treating secondary infections in Covid-19 patients, 18 antibiotics have greater than 80 percent of their supply coming out of either China, India or Italy — all places that have had production disruptions,” said Stephen Schondelmeyer, a professor at the University of Minnesota’s College of Pharmacy who is a co-leader of the Resilient Drug Supply Project, which aims to provide a detailed map of the supply chain for important drugs used in the United States.

Another factor that can affect the global supply chain is when countries ban export of certain drugs, either because of trade wars or because they want to ensure supply for their own citizens, Mr. Schondelmeyer said. India, for example, has put a ban on the exports of 26 drugs and drug ingredients, including hydroxychloroquine, an old malaria drug that is being used around the world as a potential treatment.