In this case though, it'd be American's fleeing the flooded parts of the US and squeezing into cities while the safer higher ground is settled by the influx of

In this case though, it'd be American's fleeing the flooded parts of the US and squeezing into cities while the safer higher ground is settled by the influx of climate refugees we'd have to deal with somehow anyway. Zero need for barbed wire or gates. I expect most of the dying will be from people trying to make it on their own in the areas that can't sustain populations any longer and of course the massive numbers of people dying at the borders because there's literally no way we could take in everyone who will need a place to live. 1.2 billion displaced people is just too much, even if we had more than a few decades to find homes and resources for them.