Between January 2021 and January 2024, CBP had more than six million encounters with unauthorized migrants on the Mexico-US border. Another two million migrants were detected entering the US but were not apprehended.

Many of the foreigners who entered the US illegally sought out Customs and Border Protection officers and applied for asylum. There is a backlog of three million immigration cases, including a million asylum cases, and space to detain fewer than 50,000 foreigners who are awaiting hearings before immigration judges. As a result, solo adult migrants who pass a credible fear test, meaning they have a 10 percent probability of being persecuted at home, are typically released into the US along with families with children and unaccompanied minors under 18. Immigration judges reject most asylum claims, but the backlog ensures that migrants can work in the US for several years while their children attend K-12 schools.