I know Michelangelo has already asked and answered this question, and NOL has dealt extensively with “the nation” before, but:

Nations are now defined not as races or peoples but by their possession of a state, and states are legitimate only if they express political will of a nation. The strange new idea of nation-building was born, the other side of the coin of state-building in the decolonizing world. It is a game played by given rules, above all that no other forms of political will and action were legitimate, especially wars of conquest.In outcome, the poor, the small, and the marginal gain the freedom of self-determination, the telos of independence, but their democratic rights extinguish utterly at the border. They have right of influence anywhere else.(137-138)

I have just two thoughts about this nugget of insight from American anthropologist John D Kelly, writing on the Wilsonian ideal in his book The American Game: Capitalism, Decolonization, World Domination, and Baseball. 1) The “given rules” Kelly writes of are still a factor in today’s world. You can most clearly see them via international governing organizations (IGOs) like the UN, World Bank, IMF, WLO, etc. Given rules are handed down to former colonies by IGOs not as a way to control these colonies but to guide them gently into the modern era. This may seem quaint, but this is how Wilson and his ilk viewed their rules and their fellow man in the colonies of Africa and Asia. If you think about institutions, even weak ones like IGOs, you know that the rules and ideals that such institutions were created to embody are hard to break; often a critical juncture is needed to do so. So the given rules of the international system are, I would argue, still based on condescending early 20th century notions about non-European peoples. This is partly why Scots and Catalonians are allowed to vote on their secessionist arguments while Kurds and Balochs and Biafrans are labelled terrorists or rebels, and states like Montenegro and Kosovo are allowed to enter the international system with virtually no hiccups while Kurdistan, Balochistan, and South Ossetia are ignored by IGOs and only informally recognized when an official state like the US requires an ally to fight an enemy.

2) This is hard for me to admit as a libertarian, but the Wilsonian ideal has helped to almost entirely eliminate old-school imperialism (violent conquest followed by oppressive government and extractive economic policies) from the earth.