The Mexico–United States border is the most frequently crossed border in the world, with approximately 350 million documented crossings annually. Immigration from Mexico to the United States has slowed in recent years.

The Mexico–United States barrier, also known as the border wall, is a series of vertical barriers along the Mexico–United States border intended to reduce illegal immigration to the United States from Mexico. The barrier is not a continuous structure, but a series of obstructions classified as "fences" or "walls".

Between the physical barriers, security is provided by a "virtual fence" of sensors, cameras, and other surveillance equipment used to dispatch United States Border Patrol agents to suspected migrant crossings. As of January 2009, U.S. Customs and Border Protection reported that it had more than 580 miles (930 km) of barriers in place. The total length of the continental border is 1,954 miles (3,145 km).

Mexico’s passive cooperation in allowing this mass incursion constitutes an emergency and extraordinary threat to the national security and economy of the United States. Mexico has very strong immigration laws and could easily halt the illegal flow of migrants, including by returning them to their home countries. Additionally, Mexico could quickly and easily stop illegal aliens from coming through its southern border with Guatemala.

For decades, the United States has suffered the severe and dangerous consequences of illegal immigration. Sadly, Mexico has allowed this situation to go on for many years, growing only worse with the passage of time. From a safety, national security, military, economic, and humanitarian standpoint, we cannot allow this grave disaster to continue. The current state of affairs is profoundly unfair to the American taxpayer, who bears the extraordinary financial cost imposed by large-scale illegal migration. Even worse is the terrible and preventable loss of human life. Some of the most deadly and vicious gangs on the planet operate just across our border and terrorize innocent communities.