The US Government completely laid waste to the societies of South and Central America, not to mention the Middle East South East Asia and much of the South Pacific and Africa.
In Guatemala, El Salvador and Honduras, peasants are routinely scooped up off their land by the "owners" who own the entire country and grow cash crops rather than food. Why don't the peasants own land? The natives didn't have deeds. Why is there no reform? We don't allow it.
For background look up the School of the Americas, Augusto Pinochet, Roberto D'Aubisson, Allende, Arbenz, Operation Condor, Mugabe, Diem, Suharto, Duvalier.
Why are they coming here? They have no place left.
Why have they no place left? Learn your own history.