The Mexicans are used to, and take for granted, the US as a safety valve that has prevented a violent revolution there for at least 50 years.
Think what a "positive rhetoric" on this could look like.
Wait, let me show how it's done. (Consulting social-progressive thesaurus)---
What do we want?
"To help distressed, displaced people get home safely."
"To assist presently-undocumented people in gaining a path to legal documentation and productive citizenship: in Mexico."
"To reunite in their native lands, families which had been torn apart by the tragic migration to El Norte."
"To restore the rich, multi-patterned fabric of Mesoamerican culture by reconnecting these dynamic people to their own roots in their own native lands."
"To enrich aid our Western Hemisphere co-partners by restoring to them the young, energetic sector of their population now temporarily scattered on foreign soil."
"To lay the foundation of good neighborly relations. This begins with, ”TU CASA es tu casa."
"To promote social justice: what's needed in Mexico isn't emigration; it's revolution."
OK, all that's laying on the verbiage a little thick. But see how it works?