Why an American football game played the Canadian national anthem

Many Americans at the game expressed their own frustrations with the escalating trade war, and the way it has divided the two neighbours.

For Drew Grier, an American who lives eight minutes from the stadium, "the anthem playing tonight is a core part of who we are as a border city".

At a Buffalo Sabres playoff ice hockey game in April, a microphone died while the Canadian anthem was being sung and the audience's voices filled in.

"You sang the Canadian anthem because it needed to happen," Grier said.

Canadian Blake Parnham recalled that moment: "I was sobbing watching the game at home because I felt so vindicated, that Buffalo is different."

He couldn't make it to Buffalo for the Bills home opener, but he enjoyed it from his elaborately decorated backyard in Keswick, Ontario.

Grier said that singing the Canadian anthem tonight is "not that polarising of a thing".

"If anyone is polarising it, it's coming from those outside here, because those of us here, we love Canada," he said.

But some thought it was a step too far.

"The only acceptable reason to sing that anthem would be if they were playing a Canadian team, but they don't play any Canadian teams," posted one fan on social media.

"I don't think it's really necessary," said David Waring, who attended Thursday's game.

In the end, it may all come down to simple economics.

The Bills' new home, Highmark Stadium, cost $2.2bn to build. While the population of western New York is a little over 1.5 million, the nearby Toronto and Hamilton greater metro areas is home to more than 8 million. Simply put, the team needs Canadian fans.

Gavin Kemp, who has run the NFL-Canada office for eight years, told the BBC that Canada's relationship to the NFL was "extremely important".

Asked why the Bills chose this year to play the Canadian anthem, Kemp said the team was "leaning into one of their biggest parts of their market".

Canada boasts nearly 15 million NFL fans – about one-third of the country's population, and roughly 10-15% of Bills season ticket holders are Canadian, according to the team.

"Sports really transcends all of this," Kemp said. "All this politics is kind of secondary to the fact that your team is doing fantastic right now."

Even American fans who traditionally cheer for other teams found themselves siding with the Bills.

Carol Breed, who backs the Detroit Lions, considered travelling to Highmark Stadium from her home in Battle Creek, Michigan, after she heard they would play the Canadian national anthem.

"I love our country's relationship with Canada," the 74-year-old told the BBC, adding that in Michigan the country is viewed more as a "relative".

"I just hate what Trump has done to the partnership."

She wasn't able to watch the game in person, but has found other ways to scratch her O'Canada itch.

A couple of weeks ago, Breed embarked on the two-hour drive across the border, on the recently opened Gordie Howe International Bridge, which has also stoked divisions between the two nations of late.

"We sang the US anthem until we reached halfway and then started singing the Canadian anthem," she said.