"The United States and Mexico have a close and complex bilateral relationship, with extensive economic linkages as neighbors and partners under the North American Free Trade Agreement (NAFTA). U.S.-Mexican relations are characterized by strong commercial and cultural ties and cooperation on a range of bilateral and international issues. In recent years, security issues have dominated the bilateral agenda, as the United States has supported Mexican President Felipe Calderón's campaign against drug trafficking organizations (DTOs). Immigration and border security have also returned to the forefront of the bilateral agenda since Arizona enacted a controversial state law against illegal immigration (SB 1070) on April 23, 2010, a measure opposed by President Barack Obama. On May 25, 2010, in response to rising state and local concerns about border security, President Obama authorized sending up to 1,200 National Guard troops to support law enforcement efforts along the U.S.-Mexico border. […]The 111th Congress has maintained an active interest in Mexico with counternarcotics, border, and trade issues dominating the agenda. To date, Congress has appropriated some $1.3 billion in assistance for Mexico under the Mérida Initiative, an anti-crime and counterdrug package first funded in FY2008. The Senate-passed version of, H.R. 4899, the FY2010 Supplemental Appropriations measure, would provide $175 million in additional assistance for Mérida-related programs in Mexico. The House is reportedly considering inserting additional funds for justice sectors programs in Mexico and for border security into its version of the supplemental measure. The Obama Administration asked for $346.6 million in assistance for Mexico in its FY2011 budget request, including $310 million in Mérida-related funding."
CRS Report for Congress, RL32724