Saltillo, Mexico - Over the years, a “mini-Detroit” blossomed in these desert highlands 200 miles south of the Texas border. General Motors, Stellantis and Daimler Trucks set up sprawling plants to churn out vehicles for export. Around them, a constellation of factories sprung up, with names like Detroit Diesel and Liberty Steel.

The migration of manufacturing to Mexico could undermine Trump’s promise to voters that ratcheting up tariffs on China would incentivize companies to bring production back to the U.S and give American companies a more even playing field.