You describe a phenomenon that is occurring globally, the rural-to-urban migration that is going on in the US, Mexico, everywhere. I don’t see how NAFTA has anything to do with it. Maybe I’m dense, but could you draw the dotted line for me? If anything, NAFTA should open up US and Canadian markets to Mexican corn growers.
Wow. Between Chinese electronics components and Canadian aluminum, high-value finished goods manufacturers in the US are taking a major hit. I know, because I experience it directly through work. We’re not relocating, but we’re taking a major profitability hit. I can confirm what @Shuck states below, that there are simply no alternative vendors for some components, even some high-performance ones. In addition, in highly regulated industries, you can’t just change components willy-nilly even if you want to. There’s an expensive process to qualify new components and component suppliers, as well as validating that they haven’t changed the performance of the end product.
ETA: Tariffs don’t cause exploitation. Tariffs don’t stop exploitation. At best, tariffs defray the cost of international trade (inspections, regulators, port development, security) vs. domestic trade. At worst, they exacerbate inequality by squeezing everyone but the exploiters.