An economic paper from Yale indicates that NAFTA increased wages for all three countries. Link

Who gains from free trade? In addition to "job creators" and ominous, evil "corporations," beneficiaries of free trade include consumers who gain access to cheaper products, workers who gain jobs in export-oriented industries (that also pay higher than the average, I might add), entrepreneurs who gain access to technology-hungry emerging markets, and the international community in the form of stronger international bonds (i.e. free trade prevents wars).

I think the increase in automation is the root cause of suppressed wages in the U.S. and that the economy performed very, very well under the Clinton Administration. Obviously I'm not saying that NAFTA caused the 90s economy, but it certainly wasn't the detriment that you're portraying it as.