The fact that you require a source for this statement shows how painfully ignorant most people in gee usa are of the demography of immigrants entering the usa.
Here you go. These are just the ones that are apprehended, there are varying estimates of what the percentage of apprehended vs un apprehended is, but it's safe to assume that at least 50% of the total is getting through without law enforcement intervention.
*"Migrants Deported from the United States and Mexico to the Northern Triangle: A Statistical and Socioeconomic Profile The United States and Mexico have apprehended nearly 1 million Salvadoran, Guatemalan, and Honduran migrants since 2010, deporting more than 800,000 of them, including more than 40,000 children. This report provides a demographic, socioeconomic, and criminal profile of Central American deportees and traces how rising Mexican enforcement is reshaping regional dynamics and perhaps ushering in changes to long-lasting trends in apprehensions."
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"Unaccompanied Child Migrants in U.S. Communities, Immigration Court, and Schools More than 77,000 unaccompanied minors from Central America were released to communities throughout the United States between October 1, 2013 and August 31, 2015. This issue brief examines where these children have been placed in the United States, how they are faring in the immigration court system, and how schools are adapting to their arrival."
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Unaccompanied Child Migration to the United States: The Tension between Protection and Prevention Policymakers, the public, and the media were seemingly caught off-guard in spring 2014 when a surge of child migrants from Central America reached the U.S.-Mexico border. Yet the uptick began in 2011. This report examines the causes of this surge and recommends policy solutions to advance both critical protection and enforcement goals in situations of complex, mixed flows."