The other replies missed a big issue with the tariffs - which is that you're not wrong, but tariffs basically guarantee counter-tariffs, which means that while you're no longer buying imports, you're also no longer able to competitively export. In the case of Canada, if you don't include raw resources, the US has a trade surplus, so tariffs make the inputs of your value-added-over-raw-resources local goods more expensive while also cutting down the export market.