How about cutting off all transfers of money from the US (Western Union, Moneygram, etc.)?
I think we should declare on Guatemala, Honduras, Nicaragua and all Salvador. Make them colonies if they are just going to ship their dregs anyway. Surely any governorship the US sets up in these locations will be better than what is in place. Then you can keep these foreigners there and incarcerate the criminals instead of sending them to the US. Win - win.