That's only a solution if you view populations as replaceable, that culture and shared history doesn't matter, and that nations are just arbitrary grouppings of people that can be changed at will.
Which works for the US, because it's a country of immigrants from all over the place anyway, colonized quite recently in historical terms (there are nations and cultures with 10x and 20x the longevity and far more continuity). If you start with a country with shared history and a cohesive culture, people are not seen as equally replaceable.
Which works for the US, because it's a country of immigrants from all over the place anyway, colonized quite recently in historical terms (there are nations and cultures with 10x and 20x the longevity and far more continuity). If you start with a country with shared history and a cohesive culture, people are not seen as equally replaceable.