That's an excellent point.
To that point, an important and underrated part of marketing is "fear of missing out." We just saw it in the U.S. with Caitlin Clark. A recent, albeit extreme example. Nearly 19M weren't watching her final collegiate game because they're women's college basketball fans, or even because they're Caitilin Clark fans. They were watching because that's what people were talking about and -especially general sports fans- didn't want to be "left out." Wanted to feel part of it and be able to discuss it with everyone else that was watching.
You can do that directly to Canadians, both new and old. I have the #'s (the few I could pry out of Canada,) you can say it in October, you can say it in November, etc. & etc., "over 2 million Canadians were watching the 7pm HNIC window Saturday night!" You repeat that, week after week and the people not watching start feeling left out.
And, to my point about USA/CAN combined, 9 different months a year, plenty of opportunities for selling that, especially post-football season in the U.S.,
If I was running the NHL PR account on X (twitter) I'd be hammering (example matchups) "Leafs-Bruins was the most-viewed sporting event across the U.S. and Canada last night," and then a couple days later, "Oilers-Penguins was the most-viewed sporting event across the U.S. and Canada last night." That sticks in minds, and gets repetitive. People will ignore Canada carrying that viewership, because they already do ignore Canadian viewership, and you change the narrative from "only 400k were watching" in the U.S., to million(s) were watching hockey "across the U.S. and Canada."