The trade war between the U.S. and Canada is temporarily on ice, but the hard feelings aren’t. When The Star-Spangled Banner is played before National Hockey League games in Canada, the boos still occasionally rain down. It’s made the NHL’s inaugural 4 Nation’s Face-Off tournament, which started on Wednesday, a bit awkward.

Canadian fans have good reason to feel aggrieved. U.S. President Donald Trump’s threats of tariffs have destabilized the Canadian dollar and it’s hurting the competitiveness of businesses there. Sports aren’t immune to the disruption and professional hockey north of the border is set up to take the biggest hit.

For starters, the NHL is the only major U.S.-based league that has a substantial number of franchises in Canada. While Major League Baseball and the National Basketball Association each have one team there, seven of the hockey league’s 32 clubs call Canada home.