There's a hard line between the United States and Mexico, and plenty of people who want to make it harder.
But while the efforts to build a wall on the border continue, ties between the countries keep getting stronger. That's the general argument of the book Vanishing Frontiers: The Forces Driving Mexico and the United States Together, by Andrew Selee.
He saw first-hand how Mexico, despite well-publicized problems, has grown more prosperous and more like the United States. He sees the border as a seam, not a barrier.
The author joins us with some finer points in his observations.