The left is doing their damnedest to push this lie. Unfortunately for them legislation is a matter of public record. Therefore I direct you to Public Law 107-296: https://www.congress.gov/bill/107th-congress/house-bill/5005/titles
This law passed the House with a vote of 295 - 132, and the Senate 90-9 - which included "Yea" votes from prominent left wing poster children like Hillary Clinton, Joe Biden, Chuck Schumer, and Dianne Feinstein. See for yourself: https://www.senate.gov/legislative/LIS/roll_call_lists/roll_call_vote_cfm.cfm?congress=107&session=2&vote=00249
Whatever your predilections are this was CLEARLY bipartisan legislation.
For the liberal rage mob: Please refer to Subtitle E, Section 462(g). I've taken the time to highlight the relevant text because we all know that doing an actual bit of legitimate research might offend your delicate sensibilities.
And there you have it - an underage child with no legal standing the USA, and no legal guardian to provide them care, gets put in a detention center - with the full blessing of your most prominent elected officials.
Dear leftists: Your lies are still showing.