As you point out NAFTA has generated a LOT of economic expansion in all three countries. If the US does not seek out places where products can be made at a more competitive rate, our international competitors WILL and the American company we tried to protect (via the use of tariffs for exp) will eventually lose its ability to compete on a global stage and those jobs will be lost in the long run anyway.
Given this - should countries try to protect certain industries simply to protect jobs and high wages? Why/Why Not?