Nations are surprised by the fact that humans can't do things nations can, e.g. walk across the entirety of Europe in an afternoon, and by the fact that humans can do things nations can't, e.g. disobey a direct order from their leader. They fail to understand human biology (such as pregnancy since baby nations just appear, and exactly how much injury to a human will cause death since nations regenerate), and emotions (being centuries old gives you a worldview humans would consider weird). Just play with this idea. I'd like to see more done with how different the nations must be from humans.