I guess this is a thing of them not wanting to literally rewrite the world in their fictional show. So, for visual purposes, you leave all the borders the same, so that when you toss up a 2 second graphic of a globe, everyone gets the information that you wanted them to get anyway (this is X country). If you suddenly redraw all the lines, it makes showing the audience a map of the world, a very confusing thing, that frankly will take up too much time in your show.The Falcon and the Winter Soldier (3/5)
However, how this translates into a refugee crisis and a shifting of borders doesn't make sense, and the show never takes the time to explain how it does. In fact, what we see on the show contradicts the notion of borders shifting because every map we see, whether it be of Europe, or the border of Libya/Tunisia, seems to be the same as in our world. Every flag we see for the GRC is a real-world flag, and if Madripor is a new nation that sprung up, that's never explained. I mean, I get why the show went this route (refugees are a real-world issue), but it doesn't work via analogy, and it doesn't work in-universe.
As to how it would be a refugee crisis, honestly that I find totally believable. If 50% of the population just vanished in a second, the complete breakdown of most infrastructure, globally, would strand lots of people. They would find themselves in an area that is completely incapable of sustaining them, because there is no way to provide the resources, to the people in question. Industries would start to break down within days, without regular maintenance, infrastructure like roads and pipes would start having problems. There was actually a show I recall seeing many years ago, on either History Channel (before it was pseudoscience BS), or Discovery, about what would happen to the world if humans just vanished. And it was basically "The Snap" but 100% instead of 50%. And a LOT of chaotic shit would happen within the first few days/weeks, without constant upkeep. So the idea that a massive humanitarian problem would arise, as the population contracted and reconsolidated, and had to abandon entire regions of the world, leaving them in ruin for 5 years, seems entirely plausible to me. And then, having all of those people dumped back onto society 5 years later, would cause huge problems.