"the true strategic threat to both Russia and the United States is China (not the casbah, for God’s sake): the cowboys and the Cossacks should be friends."This makes sense from an American nationalist viewpoint: superpower politics. It also makes long-term strategic sense for Russia, looking at their Siberian border with China.
If super-intelligent, incredibly-prosocial and pleasantly-attractive aliens landed in, say, Australia with a view to world colonisation - should we be in favour? They sound nicer than us. Or should we be with Juan Rico: on the bounce and looking out for the interests of the human race, come what may. My species, right or wrong.
Frank Salter had a flawed and controversial book, "On Genetic Interests: Family, Ethnicity and Humanity in an Age of Mass Migration", out in 2006 arguing that:
"In modern Darwinian theory, bearing children is only one way to reproduce. Since we share genes with our families, ethnic groups, and the species as a whole, ethnocentrism and humanism can be adaptive."But the average level of relatedness between random members of a genetically-homogeneous nation is about 1/128 (discussion here). This doesn't seem nearly enough to trigger any emotional feelings of kin solidarity, see here.
Nevertheless, there's plainly a measure of emotional solidarity underlying nationalism. It seems to work through shared cultural signifiers (appearance, dress, behaviour, speech patterns, interpersonal style, social conventions and ritual) rather than that you know your co-ethnics at an individual level and feel some nationalistic kin-warmth towards them. That emotional propensity seems also to have been selected for - you don't see it in other animals. It does, however, facilitate the building of empires, which are astonishingly good for your genes.