In this article from VICE.com we get an all too brief introduction explaining, in part, what's driving the refugees from Central America. Many of Trump's supporters won't want to acknowledge it, but what we're seeing today is a product of what former CIA analyst Chalmers Johnson called "blowback."
In simpler terms, the chickens are coming home to roost.
If you want to know the roots of this story, you can start with this book, which explains the U.S.-led overthrow of a democratically elected government in 1954.
For those of you who want to know more about blowback in the Central American context click here.