I have spent ten days of my life in Canada and I learnt of the tariffs by news reports concerning people driving to USA, loading up on milk, coming home.
Tariffs are not always stupid. But in most cases there is a better alternative.
E.g. Canada could subsidise domestic milk producers. (We used to do that in New Zealand)
There is a lot of nonsense talked about economics ("tariffs always bad" is an example) because there are strong incentives at work for the actors. It makes it very difficult for policy makers to have good, responsive, effective economic policy.
Money and politics? What could go wrong....