In my post “You Didn’t Build That: America Edition” I wrote:

We didn’t build this unbelievable American system, and it is not our private property. We don’t have a moral right to exclude other human beings—human beings like us—from the benefits of this unbelievable American system. As stewards of this unbelievable American system, we need to regulate the pace of arrival so that the system itself is not overwhelmed and destroyed, but unless this unbelievable American system itself is threatened, let us open our doors wide to others who have not had the good fortune to be born Americans.    

(“This unbelievable American system” is Barack’s phrase.) Vipul Naik and Garett Jones argue, as I would argue as well, that it is not that easy to overwhelm “this unbelievable American system” with new arrivals.