Kindly explain what you suggest the United States should do about Mexico, then.
The Mexicans know full well that the moment any controls are placed on immigration that either they pack their bags and get over to Europe quickly or they make some very quick reforms. There is no other reason that all prosperity and hope for opportunity comes to a screeching halt when you reach that southern border except that Mexico has an extremely corrupt government and system.
We cannot continue solving all Mexico's vast and growing social problems --- just because they wish to keep things just the way they are.