Most workers are better off from NAFTA (as consumers).
Only the uncompetitive part. Only those parts of industry which were less competitive left. It's good for the less competitive to be replaced by the more competitive. 300+ million consumers are made better off as a result, by the production being made more competitive, e.g., less costly.
I.e., the uncompetitive workers and companies. But 300+ million U.S. consumers are made better off, so the total destitution was reduced.
Enter Trump, who campaigned across the Upper Midwest on the message that NAFTA was “the worst trade deal in the history of the country” and that our partners were taking advantage of us.
https://www.truthdig.com/articles/did-trump-get-it-right-on-nafta-2-0/
But 300+ million U.S. consumers are better off because of NAFTA. Maybe a million or so workers are worse off, while the vast majority of them are better off as consumers.
(Leaving aside the perverse protectionist elements in NAFTA, i.e., the negative part, which probably did benefit certain favored companies and workers at the expense of consumers. But this is a minor part of NAFTA, compared to the pro-trade part.)
What's good for THE NATION? Taking care of 300+ million consumers is better for the country than protecting the uncompetitive jobs of a few and driving up costs to everyone else.
Trump's changes can be good for consumers if they force other countries (Canada) to open their market more, so that free trade is promoted, which is good for everyone.
However, they might do the opposite. The requirement forcing Mexico to increase its wages to autoworkers will make production more costly and cause higher prices to consumers. Also requirements to force local content into the production.
These artificial measures, forcing production to be done where it's more costly, and driving up the wages artificially, can only be detrimental to consumers. Trump is basically pandering to the crybabies with these requirements, i.e., crybaby companies and workers who want to be protected and not have to compete.
So don't worry. Trump seems to be pandering to the crybabies still, i.e., to the uncompetitive companies and workers, to protect the uncompetitive "jobs" and to promote the "jobs! jobs! jobs! jobs! jobs!" obsession, along with Bernie Sanders and the other protectionist demagogues.
So the crybaby workers who were being protected will continue to get some of the protection they want, at the expense of all the consumers, and to the detriment of the nation overall.
But it would be much worse for consumers if NAFTA was abandoned and worse trade barriers should replace it.
The labor unions want to abolish NAFTA altogether, to promote more "jobs! jobs! jobs! jobs! jobs!" or Babbling Bernie's "good-paying jobs" for the uncompetitive, no matter how much damage it does to consumers.
It may be true that in the long run protectionist NAFTA-bashing promotes more "jobs! jobs! jobs!" by forcing everything to be produced domestically, thus eliminating the benefits of competition and trade, but it's more important to serve 300+ million consumers than to provide babysitting slots ("jobs") for uncompetitive crybabies.