Before each of the two games that the New York Yankees lost to the Blue Jays over the weekend, nearly 45,000 Toronto fans stood silent and still as they took in “The Star-Spangled Banner,” then roared with applause as the singer approached the anthem’s final notes.
The “Yankees suck” jeers would come later, in the fourth inning on Sunday after Vladimir Guerrero Jr., the Montreal-born first baseman, hit a grand slam to put Toronto ahead, 9-0. But the American anthem was shown a reverence typically reserved for church hymns.
It was a stark contrast from February, when in response to President Trump’s threats to impose tariffs and make Canada the 51st state, Canadians began booing “The Star-Spangled Banner” at hockey and basketball games. At the time, Canadians were also starting to rally around their flag, boycott American products and cancel plans to travel south.
Mr. Trump’s threats have not let up, making this a striking moment for the Blue Jays, Canada’s only Major League Baseball team, to be dominating one of America’s most storied teams in the playoffs.
Game 3 of the American League division series will be played in New York on Tuesday. The Blue Jays have outscored the Yankees by 23-8, chased both starting pitchers after only a few innings and made the star outfielder Aaron Judge look like your next-door neighbor.
Toronto won the World Series in 1992 and ’93, and except for brief indignation when a U.S. Marine color guard unfurled the Canadian flag upside down before a game in Atlanta, political tensions were nonexistent. But this series is beginning to feel like a barometer for U.S.-Canada relations.
“It’s difficult for the average American to understand how hurt the average Canadian is by the things being said about us and at us,” said Cathal Kelly, the national sports columnist for The Globe and Mail. “There’s anger at being belittled by someone we thought was our best friend, but there is a greater sense of betrayal.”
As Toronto enters a hostile environment at Yankee Stadium on Tuesday — throughout two regular season series, New York fans booed “O Canada” — Prime Minister Mark Carney of Canada is scheduled to meet with Mr. Trump for a third time. Mr. Carney is seeking a deal to end or reduce devastating U.S. tariffs on goods like aluminum and lumber.
Whether or not he succeeds, Canadians are feeling an October enthusiasm typically reserved for the start of hockey season.
“There’s only one way we can hit back that we know the typical American will notice — sports,” Mr. Kelly said. “People who zone out tariff talk notice when the New York Yankees are getting manhandled by Canada’s baseball team.”
The Blue Jays were one of the top teams in baseball throughout the regular season, and Americans took shots. In July, the Yankees’ play-by-play man, Michael Kay, called Toronto “not a first-place team.” In September, the Baltimore Orioles’ analyst Brian Roberts irritated Blue Jays fans and players when he said: “Sometimes we had some major questions about the baseball I.Q. of some Canadians.” He later apologized.
John Schneider, the Toronto manager, said the team was now playing for something bigger than the ball club or the city.
“The atmosphere here is — you kind of have to be here to understand it,” Mr. Schneider said. “It’s something this group does not take lightly. It’s something that we as an organization do not take lightly, that we’re playing for a country.”
Roy MacGregor, who has written more than a dozen books about Canadian identity, history, hockey and politics, said that while Canada’s win over the United States in the Four Nations hockey final in February did not mean much to the average American, the Blue Jays’ advancement to the American League Championship Series over the Yankees might.
“Hockey doesn’t generally resonate in America,” Mr. MacGregor said. “The Four Nations final was a spectacle, but it mainly resonated up here. Baseball, however, really does carry across. If the Jays keep going, that’s going to start to really piss some people off.”
He added: “And don’t tell Yankees fans that the guy who replaced Babe Ruth — George Selkirk — was Canadian.”
Mr. Kelly said that until the Blue Jays won the World Series in 1992, most Canadians had focused on the nation’s long hockey rivalry with Russia. Suddenly, people believed beating America was possible.
“Doing it again has been the national goal ever since,” he said, noting that the Toronto Raptors achieved that goal in 2019 when they won their first N.B.A. championship.
“The Jays winning would be bigger than huge,” he added. “Given the current political situation, it would be the great Canadian nyah-nyah-nyah-nyah-nyah moment.”
Ernie Clement, the Blue Jays infielder who grew up in Rochester, N.Y., said being regarded as Canada’s team was “really, really special.”
“When you’re playing for a country, it’s a little bit different,” he said. “At the end of the day, we’re playing for the guys in our clubhouse. Then we’re playing for the Blue Jays organization, and then we’re playing for an entire country. There’s not another team that can say that.”