The central metaphor of roots, branches, and harvest creates the structure and thesis of the book. To explain the harvest (the explosion of Latin American immigrants in this country) we must look to the causes of such growth, the roots, which start as early as the 1500s when Spain (and later England) began colonizing in the Americas. As these colonies grew and developed, the annexing of land up until the Spanish-American War, at the end of the 19th century, ended up annexing both Mexican land and Mexican citizens; many Latin American immigrants became US citizens through conquest.

Other causes also explain the great number of Latin American citizens in this country. US foreign policies designed to protect and promote the profits of American businesses in various Latin American countries came to be the norm in the 20th century. These policies often actively supported Latin American dictators and strongmen, despite their human rights abuses, simply because these strongmen could be counted on to support American businesses. During the Cold War, the United States perceived any leader with ties to communism as being a threat to the United States; American presidents worked actively to destabilize such leaders, as can be seen in the Iran-Contra deal that worked to overthrow the Nicaraguan Sandinistas, even though the Sandinistas were the populist leaders.