Regarding the Canadian border, I think that Canadians expected that people with dual passports would choose a country and sit tight during the pandemic. Instead, it seems that those people with dual citizenship are freely and frequently flying around the world and bring variants into Canada.
Are Canadians with one passport mostly sitting tight? Is essential travel so loosely defined that in-person meetings, visiting hot zone families, and checking holiday property qualifies?
The only way to fix this problem is to tell everyone with dual citizenship that they have 2 weeks to decide whether they are Canadians first. If they want to be somewhere else, they should be required to stay there until the pandemic is gone.