As he played a chainsaw-wielding Elon Musk on “Saturday Night Live” in March, the veteran Canadian comedian Mike Myers was not intending to make a personal political statement. But when he stood onstage for the closing credits of the show, he said, “I got angrier and angrier.”

He thought about Mr. Musk’s remark that Canada is “not a real country,” and about how President Trump had called the former Canadian prime minister “Governor Trudeau” and rudely referred to Canada as “the 51st state.” He thought about tariffs, and about graffiti he’d seen in Winnipeg: “There’s no greater pain than being betrayed by a friend.”

And he thought about the legendary Canadian hockey player Gordie Howe and his famous “elbows up” response to aggression on the ice.

And so Mr. Myers, the 61-year-old star of the “Wayne’s World,” “Austin Powers” and “Shrek” films and a beloved figure on both sides of the Canadian-American border, boldly opened his down vest and flashed his “Canada Is Not for Sale” T-shirt on live television. “Elbows up,” he mouthed into the camera, twice.

“What happened came from my ankles and from my brain and from my heart, and it was not about me — it was about my country,” he said. “I wanted to send a message home to say that I’m with you, you know.”

As public acts of defiance on “S.N.L.” go, the unveiling of Mr. Myers’s T-shirt was less shocking than, say, the Irish singer Sinead’s O’Connor’s dramatic destruction of a photo of Pope John Paul II in 1992. But for the mild-mannered Mr. Myers, an expatriate who said that “no one is more Canadian than a person who no longer lives in Canada,” it was the moment the gloves came off.