give green card to undocumented people & send message to their leaders to provide basic needs & safety to citizens.

I believe that if the leaders of those countries with lot of people who migrate in U.S. have been providing basic need and safety for their citizens effectively, they will not come to U.S. Recently, we can observe that there are less people in Haiti that risk their lives to come to U.S., this could be because there are more opportunities for some of them to create their small businesses to survive. The help of many organizations that provide loans, grants, and mentors to the Haitians may be making a difference. By the same token, The President of Mexico mentioned on the Charlie Rose’s show that he is focusing on education and providing basic need to the Mexicans.
Other leaders may be doing the same for their citizens. Right now, they are more aware about taking care of their citizens.