There are a lot of Canadian products that are only "Canadian" products. Even something like Old Dutch chips -- which (when sold in Canada) are made in Canada by Canadian employees using Canadian ingredients... Is a privately held business owned by Americans. These companies are effectively part of the funnel of capitalism -- profits are extracted from Canadians and sent elsewhere.
And yes, I get it, sometimes foreign investment is nice. Canadian companies invest in foreign markets too. But when you're in a trade war with your neighbour, you want to know not just where it is made, but where the money flows.
Even buying Canadian products at Walmart Canada (an somewhat independent Canadian subsidiary of Walmart in the US) still feeds some of the profits on the sale to the US.
Capitalism is a funnel. Too much profit is funnelled south.