The potential of Mexico, Canada and the United States is enormous. We have a combined population of half a billion people; peaceful trade-friendly borders that are the envy of the world; the prospect of energy independence is within reach and will change the geopolitical situation of United States; we do a trillion dollars in trade among the three countries; more than 18,000 American companies are involved in foreign direct investment in Mexico and Canada; an increasing number of Mexican companies are creating jobs in the United States.

Not only are the numbers of migrants entering the United States at the lowest levels in a generation, but they are now largely Central American. Four out of five border-crossers detained in South Texas are Guatemalan, Honduran or Salvadoran. They are driven by violence and poverty in their home countries and the desire for family reunification.

America should be working more with the Mexicans to prevent the flow of guns going south into Mexico that have fueled so much of the violence there, and the smuggling of cash and the money laundering that transnational criminal organizations have instituted in North America, including in the United States.

I think there's no question that the barriers, the fences and in certain urban areas, the walls, have had an important effect in terms of increasing the manageability and the security of the border. But in fact as Secretary of Homeland Security General John Kelly acknowledged at his confirmation hearing, walls and barriers alone are insufficient to insure security.

In the last generation we've moved past a U.S.-Mexico relationship that while friendly on the surface, and demilitarized for the most part, really was not a genuinely cooperative relationship. As a result of the U.S.-Mexico War in the 19th century, and the treaty of Guadalupe Hidalgo in 1848, half of what was Mexico was severed and became much of the western part of the United States. To add insult to injury, most Americans never knew that, and most Mexicans have never forgotten it.

The cry of "Make America Great Again" reflects accurately that, after the fall of the Soviet Union, the sole superpower status of the United States is coming to an end. For the first time since the second World War, we are not the sole dominant economy in the world. In large part this is because of the success of policies followed by the United States to create an environment, a peaceful period in history in which economies could grow and countries could benefit.

In the last two years, the Mexicans have detained nearly 400,000 migrants whose intent was to come to the United States. The Mexicans return the detained Central American migrants by bus or by air to the countries they come from.