Why you cannot see American commercials during Super Bowl
When watching the Super Bowl in Canada, the Super Bowl broadcast will feature entirely Canadian Super Bowl commercials. This comes from a Supreme Court of Canada ruling in late December of 2019 which aims to protect the rights of Canadian broadcasters and keep advertising dollars in the Canadian market.
Why we don't get the American ads during the Superbowl
The Supreme Court of Canada ruling in December of 2019 was to promote local broadcasting and local creation. The practice is called "simultaneous substitution" and allows for the Canadian broadcaster to air Canadian ads but keep the program the same. When a substitution occurs, you see the signal, including the Canadian commercials, on a US channel.
Note: Even though the American commercials may not appear on the broadcast, most of the Super Bowl commercials will be uploaded online, in some cases even before the big game.