Illegal immigration is a thorny question. Obviously in an ideal world, people would go through the normal legal process and not try to sneak through. However, we must admit that American foreign and domestic policy bears significant blame for the large unauthorized population. Free-trade agreements have done significant damage to the economies of Mexico and Central America (especially in agriculture), creating a large pool of people desperate for work. Second, the legal immigration process is a janky, unfair, and expensive nightmare of paperwork.
More important, America also directly destabilizes countries in Latin America. U.S. drug policy powerfully fuels gang violence in the region, by creating a hugely profitable black market through drug prohibition, and by pressuring those countries to attack drug cartels with the military. The result is a horrifically bloody free-for-all as drug gangs fight for control over the drug trade. The violence is so bad — El Salvador and Honduras have the highest murder rates in the entire world — that it destabilizes the very state itself in many countries. Then there’s the U.S. history of direct military intervention in the region, including multiple coups, the arming of death squads, and the creation of puppet states for rapacious fruit companies. As recently as 2009 the United States enabled a coup d’etat in Honduras, though not directly.