The president keeps insisting that the borderline between the U.S. and Canada is “artificial.” It’s worth asking why he’s fixated on this.

Canadian Prime Minister Mark Carney visited the White House on Tuesday for his first talks with Donald Trump and bluntly told the US president that Canada would never be for sale. Carney won the April 28 election on a promise to stand up to Trump, who has imposed tariffs on some Canadian products and often muses about annexing the country.