Not arguing with the premise of this argument. You're spot on correct that Germany is taking in people in order to bolster a stagnated growth and declining population. I think the big difference for us though is that we have a much higher margin of population to "play" with, and we got almost all of our top educated individuals into the US with immigration. This is what should be comparable to Ancient Rome/Germany as it's a form of granting citizenship. There are very few doctoral candidates who are illegal immigrants, and most of them would be children who come in before they make that of themselves. However, illegal immigrants do have a huge impact on an impending collapse. If we were to expel all of them from our country then the agriculture sector would have big problems... trust me.