Novo Nordisk will lose billions because it didn't pay a couple hundred dollars

Not just Canadians. According to the source for the article, Canada is the second largest market for semaglutide. Canada has a decent fraction of obese people, but in terms of absolute numbers it's far from 2nd. This can be explained by the fact that lots of Americans are already getting their semaglutide from Canada. Once the patent expires next year and the price drops, that number is going to go up substantially.