Suppliers are waiting to see whether President Donald Trump will challenge the fundamental assumption that some auto parts can't be profitably produced in the U.S., even with a 35 percent tariff.
Products with high labor content, such as wire harnesses, small motors, cut-and-sew seat components and electronics, typically are produced in low-wage countries such as Mexico.
That's also standard procedure for automakers in Japan and Germany, which get their labor-intensive components from markets such as Poland, China and Vietnam, said Kristin Dziczek, director of the Industry, Labor & Economics Group at the Center for Automotive Research.
"Every major auto production region has a Mexico," Dziczek said. Suppliers choose low-wage countries to produce "commodities that aren't very complex to manufacture. That stuff is almost all gone" from U.S. factories.
The Trump administration's decision to renegotiate the North American Free Trade Agreement already is causing big headaches for suppliers, which cluster their factories around their customers' plants.
Ford Motor Co. recently killed plans to build an assembly plant in San Luis Potosi, Mexico. Meanwhile, Toyota and BMW say they will complete construction of their Mexico plants, although suppliers might be tempted to question the future of those projects.
But even if the Trump administration tears up NAFTA, it doesn't seem likely that all suppliers in Mexico will return to the United States.