Well, since here in the good ol' USA you can apparently sue someone in Aargentina for acts committed on Argentinian soil against Argentinian citizens some decades ago, I'd not be surprised at all to see Canada allow suits against operators of American websites for allegedly libeling canadian citizens. It's not near as much of a stretch, since the internet extends to Canada.
There is already a precedent for this. Conrad Black was allowed to sue an American website under Ontario defamation law for words they published in the US.
Because of the internet we, literally, are all in this together.
The U.S. Supreme Court has shut down most of those lawsuits (see, e.g., Daimler v. Bauman decided by SCOTUS this month).
I'd not be surprised at all to see Canada allow suits against operators of American websites for allegedly libeling canadian citizens. It's not near as much of a stretch, since the internet extends to Canada.
No doubt that Canada can do that but, unless the American defendant has assets in Canada, it won't do the plaintiff any good. Under the SPEECH Act (passed unanimously by Congress in 2010 and signed into law by Obama), a foreign-court's libel judgment cannot be enforced in the United States unless the foreign country's libel laws are at least as protective of free speech as U.S. law.