They're on recess now, but hopefully when they return, they will move quickly to repeal Country of Origin Labelling.
Otherwise what ever products Canada and Mexico choose to levy the tariffs on, they will import a whole lot less of from the United States.
Apparently it's my understanding it's pretty well wide open.
Both your country and Mexico can choose what products to place the tariffs on and so, for Canadian consumers, it may mean a bit higher prices for those goods but, certainly for U.S. exports it could mean dramatically lower shipments from the U.S. to Canada so it could be terribly disrupting for U.S. businesses which is why I'm hoping that the U.S. Senate will move quickly to eliminate Country of Origin Labelling.
Retaliatory tariffs could come into effect as early as late summer, or early fall.
Source: Farmscape