Well damn. This is deep. But I think it would matter what said "Nation X" is doing. If they're attacking us and being generally unpleasant , then I know I wouldn't want them in my world. But if they're peaceful, trading with us, and all good feelings around, we shouldn't FORCE them, but rather...encourage...them to live with us. When you asked about someone coming from the future/fantasy world, I think it's necessary that he/she changes to fit, because we as humans, have a fear of what we don't know. We don't fear all the same thing, but we fear the unknown. The last thing this poor being ripped from his world is some person freaking out and having large riots and shit like that.