Trump's announcement that the United States is pulling out of the Intermediate Range Nuclear Forces Treaty may be a sign that the United States in prepared to rapidly concentrate it's military forces along the Mexican border, and perhaps cross into Mexico.
The Intermediate Range Nuclear Forces Treaty requires the United States (and Russia) to use a hot-line to immediately explain mass concentrations of military forces. Trump may not want the obligation to explain his military approach to Mexico.
Mexico is the world's second deadliest war zone. Over one million Americans live in the Mexican State of Nuevo Leon, and the death toll of American could be in the hundreds of thousands, and damage to American companies in the millions of dollars, if the capital city of Monterrey falls and cartels and mobs target Americans.