As images of protests in Southern California have flooded television and social media in recent days, a key question has emerged: Why are so many protesters carrying Mexican flags at an American political protest?

The sea of red, white and green Mexican flags at anti-deportation protests this week in Los Angeles has been seized upon by conservatives who argue that the demonstrations are inherently un-American, causing some protesters to consider leaving them at home.

Photos of masked provocateurs waving Mexican flags atop burning Waymo taxis spread instantly across conservative social media this weekend. Republicans pointed to them as a prime example of why President Trump called in the National Guard and how immigration had gone too far in California.

“Look at all the foreign flags,” Stephen Miller, the deputy White House chief of staff and the architect of Mr. Trump’s domestic agenda, said Sunday on X. “Los Angeles is occupied territory.”

To many Americans, including those on the left, it might seem a bad strategy to fight deportations of undocumented immigrants by waving the flag of another country.

But protesters said this week that they see the Mexican flag as a symbol of defiance against Mr. Trump’s immigration policies or of solidarity with other Mexican Americans. The flag has become so ubiquitous in recent decades that it is a part of the Southern California landscape, adorning pickup trucks and flapping from bridges. Few mass gatherings occur in the region without a Mexican flag or two, from weekend soccer matches to Los Angeles Dodgers championship parades.