Market forces are merely a means to an end. The U.S. Government should only permit them to operate to the extent that has the effect of making the majority of Americans more prosperous (which it usually does). Do trade policies that have the effect of making Mexico richer have the effect of making the median American richer? I don't know the answer to that. Americans seem to think not.
The US Government should do what is best for the country and it's surroundings in the longer term, not what is best for isolated groups of Americans in the short term, and it was doing mostly that.
Trade policies that only work to the advantage of one of the trading partners are bad for everybody in the long term, they need to be win-win to really work.
> Americans seem to think not.
Americans by and large seem to think things are reasonably ok, as they should given the fact that the country is doing amazingly well. All this talk of doom and gloom is mostly a stage show set up to galvanize the votes of the dis-enfranchised.
It's a natural reaction: who cares if the country as a whole on average is doing much better if your little pocket of it is doing much worse? Who cares about the world as a whole doing better if your part of it is sliding backwards.
Adapt or die is easy to say when you're the one that has adapted, it's a lot harder if you're likely in the part of the population that will simply die.
And that's the heart of the problem, not whether or not the median American is getting richer, if that were the case nothing should have been changed because that was exactly what was happening already.
Mexico was getting wealthier, people were more likely to return to Mexico.
Ironically this whole border wall + move jobs back to the USA thing has made the chances of illegal immigration from Mexico to the USA for a given individual go up rather than down.
As for who would make Mexico wealthy: that would not be the US government but market forces and corporations, the things that America has historically been such a huge proponent of.
But that's all gone now, it's the new times now, market forces are bad, companies need to be 'incentivized' to move their production back to the home country and all those illegals need to rounded up and sent back.
Government would have a hard time achieving the goal of making Mexico wealthy but they sure can do a lot to make things worse which will put upwards pressure on Mexicans to seek a better life elsewhere.