This caravan is going to be stopped on American soil. As soon as ICE detains them, they are compelled BY LAW to bring them before a judge who will them a date when next to appear.
Mexico could have stopped them but refused so Trump is retaliating against Mexico and urging the feckless McConnell to invoke the nuclear option to undo fix the law.
Assuming that they do...
Sin Aqua signs along the border.