In France, a strong belief that the French would culturally reject the practice — and confidence that masks could be imported quickly if needed — has contributed to a desperate shortage. In the past decade, France’s formidable national stockpile of masks shrank from 1.7 billion to 150 million at the outset of the current pandemic.

The debate over the simple face mask has sometimes evolved into a larger discussion over the role of the individual in society, pitting the West’s individualism against Asia’s collectivism.

President Trump appeared to embody that ambivalence when, even as he announced that the Centers for Disease Control and Prevention now endorsed widespread mask-wearing, he said he would not wear one himself.

Frédéric Keck, a French anthropologist specializing in pandemics, said that, in the West, mask-wearing was seen through an individual’s perspective.

“‘There’s a virus outside, so I wear a mask only to protect myself,’” Mr. Keck said, “whereas collective reasoning, in Asian societies, is to say, ‘I wear a mask to protect others.’”

The difference in mind-set is a crucial one given the nature of all but the highest-grade masks: Masks are believed to have some effectiveness at protecting the wearer, especially in crowded spaces, but are most effective at reducing the risks that the virus will be spread through coughing or talking.