In the 1990’s politicians trying to explain away all of America’s ills, without blaming American voters or accepting their own fair share of blame, turned their attention towards the southern border. The ebb and flow of migrants across the border, which had been occurring since the Treaty of Guadalupe Hidalgo established it at its present location, was recast as an invasion. The invaders (who were, conveniently, ineligible to vote) were blamed for rising crime and failing schools, unemployment and overstretched social services. Clearly, the invasion must be stopped before the nation was overwhelmed.
Time to call in the troops and wall off the border.