MEXICO CITY

NOWHERE in the United States Constitution is there any mention of Miss U.S.A. She has no authority to declare war. She does not build border walls or round up undocumented immigrants. Those things are left to others, none of whom wear a sash.

But that fact seemed to get lost during the recent Miss Universe pageant, when Mexicans greeted Rachel Smith, Miss U.S.A., with one chorus after another of boos. Pageant officials said Ms. Smith, 22, was rattled by the denunciations, which echoed other booing she had received during her monthlong stay in Mexico, notably when she showed off a sleek, white Elvis outfit as her national costume on a runway on one of Mexico City’s grand avenues.

On pageant night, the wrath continued. As Ms. Smith was chosen for the final five, despite an awful fall in her evening dress, the crowd grew more boisterous, especially because Miss Mexico, Rosa María Ojeda Cuen, had been eliminated. Donald Trump, who owns the pageant, said he was nervous the audience might storm the stage. “The level of hostility was amazing,” he said, comparing it to the fury on display at the end of a disputed prizefight.

Mario López, the TV actor who was the show’s host, did his best to calm the crowd during a commercial break. “I said in Spanish: ‘Hey, listen, Mexico, the world is watching. Let’s show the world we’re really good hosts,’ ” he recalled.