Nationalism really comes down to a debate between Kant and Hegel. I am on the side of Kant in this, but I think Hegel also had some good points.  I am not sure how to reconcile them. You can see the side of nationalism in Howard Bloom's, The Lucifer Principle. But the draw backs of the system in the USA was brought to print by Allan Bloom's masterpiece, The Closing of the American Mind.

[I should say here that I tend to be on the ide of the Kant-Fries school of thought that you can see in the blog of Kelley Ross] And I also think that my very good impression of Hegeli more based on my  reading of his Logic of the encyclopedia. That is a masterpiece. But the way he elevates the "State" in the Phenomenology is really hard to digest.