Singer Chantal Kreviazuk changed the lyrics of the Canadian national anthem during the 4 Nations Face-Off championship game between the US and Canada on Thursday, adding further fuel to a contest already layered with political tension.

Canadian hockey fans began booing the American national anthem at Bell Centre in Montreal when Team USA played there on Saturday — sparking three fights to break out in the first nine seconds of the game, which the US won 3-1 with Canadian Prime Minister Trudeau in attendance.