George Recine, a Boston advertising executive, knew exactly where to eat lunch last week during a business trip to Philadelphia.

“What better place to stop by than Goldie?’” he said.

Mr. Recine, 45, had read reports about a protest there a few days earlier that Pennsylvania’s governor and the White House had condemned as antisemitic. A crowd carrying Palestinian flags had gathered in front of the popular falafel restaurant, co-owned by an Israeli-born chef, and chanted, “Goldie, Goldie, you can’t hide, we charge you with genocide.”

All Mr. Recine knew was that the owners had donated restaurant proceeds to an Israeli medical nonprofit organization that has supplied that nation’s troops with toiletries and gear in the Israel-Hamas war. He showed up to buy a falafel as a statement. He didn’t think an American restaurant serving Israeli food should be a target.

Like the protesters, Mr. Recine was participating in a longstanding American practice: If you want to ignite social change or protest a war — or even just air an opinion — do it at a restaurant.

Why? Unlike many other businesses, restaurants often proclaim their nationality, ethnicity and sometimes the owners’ political views. And at a time when Americans of differing political tribes often stay in their own corners, a restaurant can serve as a de facto town square.

“Food is very accessible and has a very low barrier to entry, so the restaurant becomes a proxy for whatever your feelings are,” said Johanna Mendelson Forman, a professor at American University who teaches a course called Conflict Cuisines that examines the nexus of food and war.

Food in America, she said, has always been political.

During World War I, many Americans refused to patronize German restaurants or beer gardens, an import that had proliferated in the late 1800s. (New York City had more than 800 at one point.) Drinking beer was such an expression of German identity that to do so was portrayed as unpatriotic.

Nearly a century later, French fries served as another barometer of American patriotism in 2003 when France opposed the U.S. military plan to invade Iraq. Restaurant owners poured French wine into the gutter and renamed French fries freedom fries.

After Russia invaded Ukraine in February 2022, dozens of people waited in the bitter cold to eat pierogies and borscht at the 70-year-old Ukrainian restaurant Veselka in the East Village of New York. The Russian Tea Room, founded in 1927 by members of the Russian Imperial Ballet who were escaping communism, lost business to a boycott. Members of the staff were harassed online.

Ruth Reichl, the food writer and former New York Times restaurant critic, said that in an increasingly fractured society, restaurants and the people who run them function as a sort of family — with many of the flash points that one might see among relatives.

“Restaurants are the heart of the community,” she said. “In moments like this they become a place where our deepest emotions play out.”

Restaurant-centered political action can be both ineffectual and short-lived. Americans seem to love French fries more than ever, and the crowds at Ukrainian restaurants have thinned.

But world events can have a lasting effect on businesses. In the days following the 9/11 attacks, restaurants serving Middle Eastern food were attacked and closed.

Chinese restaurants emptied out at the start of the pandemic, when little was known about Covid’s origins and President Donald J. Trump fueled anti-Chinese sentiment by calling it the Wuhan virus or the “kung flu.”

Grace Young, the cookbook author and culinary historian, ate at Wo Hop, the second-oldest restaurant in Manhattan’s Chinatown, the day before the city lockdown began. The manager told her that 70 percent of the neighborhood’s restaurant owners had already decided they couldn’t go on without customers and closed.

“It was a really heartbreaking situation,” she said. “What happened to Chinatown is people just didn’t discriminate against the restaurants. They discriminated against every business in Chinatown.”

Many restaurants never reopened, and business in Chinatown hasn’t returned to pre-Covid levels, she said.

Because restaurants are one of America’s most accessible cultural products, they have been barometers not only for social change but for cultural understanding. Food becomes a vehicle for public acceptance of political ideas.

Americans skeptical of both the communist Chinese government and Chinese food beyond chop suey watched President Richard Nixon eat Peking duck and steamed chicken with coconut during his visit to China in 1972. The trip stabilized a precarious diplomatic relationship, and the cuisine took off in the United States.

Wyche Fowler, a former U.S. senator and ambassador to Saudi Arabia who also happens to like good food, was fond of saying that you could always tell where the latest global conflict was taking place by looking at the list of new restaurant openings in Washington. Indeed, restaurants serving the food of an immigrant’s homeland serve as both a point of entry into the American economy and a place to gather.

Restaurants have been the locus for civil rights battles. In 1960, four Black college students sat down at a Greensboro, N.C., lunch counter reserved for white people. They were working under the simple notion that anyone should be able to order a cup of coffee anywhere.

When they were asked to leave, they stayed. For six months, they and other protesters who joined in endured racial slurs and food dumped on their heads. The action inspired other sit-ins and helped fueled a powerful new chapter in battle to desegregate the South.

More recently, chefs themselves have actively brought politics into their restaurants. That’s in part why marchers decided to protest at Goldie, one of several restaurants co-owned by Michael Solomonov, whose sales on Oct. 12 were donated to the Israeli nonprofit. (In a letter to the staff obtained by The Philadelphia Inquirer, Mr. Solomonov said he was unaware that the Israeli organization was providing the army with ambulances and medical supplies.)

In November, support for Israel also caused a deep public rift between the staff and the self-identified Zionist owner of an Upper East Side coffee shop that drew international attention.

Not all the chefs’ political involvement is as controversial. In 2012, the James Beard Foundation began its Chef Bootcamp for Policy and Change to train hundreds of chefs to influence national and local food politics.