The ‘Mexico’ label was fair to use in the 1990s, but I think in the past twenty years....a large segment of the incoming crowd are from Honduras, Guatemala, El Salvador, and Belize.
You can also note in recent weeks that African migrants have been noted crossing the border. Rumors suggest that freighters are carrying across the Atlantic for a price, and a smuggler route is being developed. Wouldn’t surprise me in a year to see 3,000 Africans a month crossing the border using this route.
Mexico’s economy specifically counts on the wire transfers of billions
You are correct that illegal immigrants aren’t exclusively Mexican or possiblt even majority Mexican. Extrapolate the financial receipts of Mexico to see just how big an issue this is.