“We don’t want any more closures, but our numbers are going through the roof,” Dr. Cameron Kaiser, the public health officer in Riverside County, Calif., said. “Please don’t mix households, even if you think everyone is healthy, and instead celebrate the holiday with the people you live with. We started seeing more and more cases after Memorial Day and we can’t afford another jump after the Fourth of July.”

The cancellations have lent a sullen tone to the typical listings of Independence Day events: “What Can You Do This Fourth of July in Idaho?” a headline asks on the website of a Boise TV station, before suggesting ways to socially distance while celebrating. At the same time, the anti-racism street protests that swelled across the country after George Floyd died in police custody on Memorial Day have prompted more people to question whether they should celebrate the holiday at all.

In Atlanta, Scotty Smart, 33, the founder of a nonprofit group called the Smart Foundation, said he had been asked to speak at “Forget the Fourth” events being held around town.

“When you look at the history of July 4, we weren’t necessarily free, so how can we celebrate our independence?” Mr. Smart said, speaking of his fellow African-Americans.