It could cripple auto manufacturing in North America. . .

“Much international trade is the result of long-term planning. To create something like the modern North American auto industry, a deeply integrated system in which various components of a finished car may be manufactured in all three countries, with parts sometimes crossing the border seven or eight times, businesses needed to make a lot of cross-border investments and carefully restructure the geography of their production.

“They were only willing to make those investments and engage in that kind of long-term planning because NAFTA gave them confidence that more or less free trade in North America was a settled issue. Now, suddenly, it seems that this confidence was misplaced.”

Paul Krugman, “How to Damage U.S. Manufacturing”

Why the change in confidence?

Tariff threats.