"Central America needs the equivalent of the Marshall Plan."
We can't even afford our own bills let alone supporting other countries. We are BROKE! BUSTED! BANKRUPT! We just ain't got the cash to bail out the world any longer, nor can we, or should we, police it. If we don't get our own financial mess straightened out, we are going to be in the same mess those countries are. Our responsibility is to our citizens and we are NOT doing that job.
Close and control the borders, period.
Either we help these countries reform or you ain't seen nothing yet. Reform need not cost a lot of money. Central America and Mexico must be moved toward better economies. We have a vested interest in their success. It would go a long way if the political class in these nations resolved to modernize business and mounted a serious, prolonged campaign to subdue violent gangs and drug cartels. Right now, Mexico might rightly be seen as a narco-state where government isn't really in control of events.