NAFTA & Political Economy of Migration is a helpful article by Collin Harris, broadly outlining how NAFTA, other neoliberal policies, and border militarization have shaped the conditions for migration from Mexico to the US:

“NAFTA finalized the restructuring of the Mexican economy that began in 1982. As Mexico was “locked in” to the neoliberal economic model, peasant farmers and assembly plant workers sought economic refuge in the country directly to the north, the center of the world’s economy. As “free” market policies pressured the state into cutting budgets for social services, Mexican communities were left with few options. Displacement of Mexican workers is the defining legacy of NAFTA-era Mexico while U.S. industries benefit from “illegal” migrants who demand much less than their U.S. counterparts in terms of wages, benefits, and legal protections. In 2001-2002, while the American economy was shedding millions of jobs, Mexican migrants arrived in staggering numbers. Currently, the vast majority of international migration in the global economy is forced migration.”

-Collin Harris