I liked your story, but feel like it missed something by not mentioning colonialsm, which is still very much practiced by the US, and actually all countries by the energy-unsustainable system of profit, after the UK being arguably the original marketers of it, after maybe the Romans. How can we be surprised that if we hadn't impoverished and made their countries less safe by imposing war and grinding poverty on them, they would not be driven to come to the countries who effectively robbed them of the wealth they should have had.
So in a way, massive immigration is Karma. What went around has to go around. We have to make the best we can of it, hopefully learning the lesson of how to stop it all from repeating until the planet burns.