Europe is currently pretty much ordered itself into nation states. It required some bleeding over the centuries. If you look at Swiss and Germans, they can hate each other and be internally fine. Both are using 2% of their GDP in defense to fend of each other proactively. There is balance of power, which result very little violence.
Now if both countries would import so much people from middle east that they would constitute something like 30% of the population of each country. Now ethnic Germans and Swiss seem to be "the same group" compared to Muslims. If shit hit's the fan, there is new pressure to readjust the borders. And move the people. Usually that stuff causes bleeding.
You could say that "if" is completely unrealistic right now. I agree. Nothing that has happened in Europe during past 15 years really warrants any policy change regarding immigration. The point was largely theoretical, just like your island.
Now if both countries would import so much people from middle east that they would constitute something like 30% of the population of each country. Now ethnic Germans and Swiss seem to be "the same group" compared to Muslims. If shit hit's the fan, there is new pressure to readjust the borders. And move the people. Usually that stuff causes bleeding.
You could say that "if" is completely unrealistic right now. I agree. Nothing that has happened in Europe during past 15 years really warrants any policy change regarding immigration. The point was largely theoretical, just like your island.