Unexpected shocks prevented the deal from reaching its full potential.
Both the peso crisis of 1994-95 and the global financial crisis dealt blows to trade between the two countries.
So did the American border controls introduced after the attacks of September 11th 2001, which raised the cost of moving goods and people.
The rapid, disruptive growth of China also interfered with North American integration.
The Chinese economy, accounting for more than 13% of global exports and around 25% of global manufacturing value-added, exerts an irresistible pull on global supply chains.
Nor is NAFTA chiefly responsible for the woes of the American worker.
In a recent essay Brad DeLong, an economic historian at the University of California, Berkeley, reckoned NAFTA might be blamed for net job losses of the order of 0.1% of the American labor force—fewer jobs than the American economy adds in a typical month.
Even without NAFTA, manufacturing jobs would have dwindled.
The strong dollar and better transport and communications technology made it more attractive to produce abroad.
Automation hastened the persistent long-term decline in industrial employment that is familiar in all rich economies— even in export powerhouses such as Germany.
Most important, the failure to agree a trade deal with Mexico would not have altered North American geography.
Mexico shares a 3,200km-long border with the world’s largest economy.
It is almost inevitable that America will be Mexico’s largest trading partner (America currently accounts for more than 70% of Mexican exports and more than 50% of its imports) .
Deep familial and cultural ties across the border shrink the distance between them even more.
Mexico cannot help but be critically dependent on its neighbor’s economy.
And America unquestionably benefits when Mexico, which has the world’s tenth-largest population and 15th-biggest economy, is more prosperous.
A richer Mexico would buy more American goods and services and provide more ideas, talent and innovation.
It would also be better placed to manage migration, and a stronger diplomatic partner.
Eliminating tariffs on Mexico would not instantly transform it into Canada, but the notion that higher trade costs between the two economies would serve American interests better is, at best, short-sighted.
No wall can insulate America against events to its south, and Americans’ own well-being is intimately linked to the welfare of their around 125m Mexican neighbors.
It is hard to blame Americans for seeing globalization as a zero-sum affair.
Stagnant pay, rising inequality and government complacency as industrial regions suffered long-term decline have obscured the benefits of trade and created fertile ground for populists.
As a result Americans feel let down by NAFTA.
Yet NAFTA has itself been let down by American leaders, who neither made the case that higher living standards are a positive-sum game, nor allowed the benefits of growth to be broadly shared.
If the upshot is the disintegration of the North American economy, those on both sides of the Rio Grande will be worse off.