Last I heard was that we import 20% of our products needed from Canada. Raising the tariffs allow competing USA made products to be equal or less in cost. This increases production, therefore reducing our costs to produce them internally. It also increases employment here in the good ol' US of A.
In my opinion, every country should produce to its fullest abilities, and if not, they need to pay the piper.
I'm still steaming that Saudi Arabia has prohibited hay farming in their own country, because of the excess water usage. This causes that country to purchase farms in Arizona and California, with unlimited water, to produce hay, which 100% is exported back into Saudi Arabia. This has never been fair, and I support banning other countries from buying land in the USA.