News that the Trump administration is mulling new tariffs on imported vehicles and auto parts hasn’t yet wrecked Asian car makers’ share prices. It has, though, driven the U.S.’s trade policy even further off-road.
Sure, investors in major Japanese and South Korean car makers were rattled Thursday: The likes of Toyota and Hyundai tumbled around 3% after the Commerce Department said overnight it is considering the new tariffs on national-security concerns. But given the importance of the U.S. market to these firms—and the fact...