If Mexico were to detain and deport 3rd country nationals as I discussed earlier, I would expect us to fund it. Conversely, it would also behoove Mexico to to stay on the good side of its neighbor and number one trading partner.
As for the enforcement of the 1996 Immigration Act’s “remain in Mexico” provisions pending adjudication of asylum claims, no one expects Mexico to “House” them - the migrants are on their own and honestly the Mexicans share plenty of blame for them being there. First though it is widely ignored, under both US and international law those seeking asylum are supposed to apply for asylum in the first safe third country. So someone fearing persecution in Guatemala is supposed to apply for asylum in Mexico not skip through 1, 2, 3, 4, countries until they get to the one they want. Mexico aggravates this by giving 3rd country nationals 20 day transit visas if they say they intend to go on to the US. if you dump your trash in my yard why wouldn’t I dump it right back ?
Example- a Honduran family enters Mexico illegally, is apprehended and Mexico gives them. transit visa letting them cross Mexico legally as long as they leave in 20 days. They then go to the border. They then either cross the border illegally and surrender to the border patrol, or what is less well known but very common, they walk up to a U.S. port of entry with no documents as say they want asylum. They way things have been done, even though congress tried to stop it in 1996, is they are processed, temporarily detained and then “paroled” into the U.S. for “public benefit” the “benefit” being them attending the their immigration hearings. Talk about a self licking ice cream cone.
A stranger knocks on your door and asks if they can live in your house because of a a tale of woe. Do they wait outside while you check their story or do you let them move in and check later ? you then find out that the neighbor who has been dumping their trash in your yard refused to let them stay in their house but instead told them to come to yours.