The flurry of executive orders issued by Donald Trump on his first day back as president showed the high priority he places on making America’s borders less porous. His efforts to “repel the disastrous invasion of our country” by migrants and drugs from Mexico and Canada may soon include stemming the passage of cars. A promise to impose sweeping tariffs on “day one”, including a 25% levy on goods from the two countries unless they do more to stop the flows of people and illegal drugs, was pushed back, but only to February 1st. Whether tariffs are imposed then or at a later date, the consequences for the car industry would be immense.