Mike Bowen, whose company, Prestige Ameritech, makes masks in a factory in North Richland Hills, Tex., said that he told officials in the Bush, Obama and Trump administrations that about 95 percent of surgical masks are manufactured outside the United States, including by American companies that moved factories overseas to reduce costs. Mr. Bowen said he had repeatedly told federal officials that American hospitals would be at the mercy of other countries in a pandemic.

“Aside from sitting in front of the White House and lighting myself on fire, I feel like I’ve done everything I can,” Mr. Bowen said. Recently, Mr. Bowen said, his company has been fielding roughly 100 calls a day from hospitals and others desperate for more masks.

Other American companies are finding their supply chains frozen.

In its factory in Charlotte, N.C., Strong Manufacturers has three L-shaped machines that are set up to churn out about 70 masks a minute, or roughly 9 million a month.

But the company sourced the raw materials for the masks from a supplier in Wuhan, China, where the coronavirus outbreak started. Now, the goods aren’t coming.

“Our materials were ready to ship from Wuhan, and they got hung up on the dock as soon as this started,” said Alan Bagliore, the chief executive of Strong Manufacturers. He said orders from other suppliers aren’t expected to arrive for up to four weeks.

Companies and individuals with no experience making masks are trying to fill the void.

Lauren Streicher, a surgeon in Chicago, has started using her home sewing machine to make cloth masks out of elastic bands, wire and material donated by a local fabric store. She said she could produce one every five minutes. On Saturday, she posted an instructional video on YouTube so others could do the same. “They don’t have to be perfect,” she said. “This is about making something practical, quick and functional. Oh, and they’re washable.”

In Los Angeles, Dov Charney, the founder of Los Angeles Apparel and former chief executive of American Apparel, in recent weeks devoted the majority of his 150,000-square-foot factory to manufacturing surgical masks and hospital gowns. The company started selling and shipping masks in mid-March; it is ultimately hoping to produce 300,000 masks and 50,000 gowns a week.