Nationalism is a young doctrine, birthed as much by the turmoil following the French Revolution as by any debate among the philosophers. In effect, it's a post hoc rationale granting new types and uses of political power to the State.
Unfortunately, educating people about phenomena that are counterintuitive, not-so-easy to remember, and suggest our individual lack of human control (for starters) can seem like an uphill battle in the war of ideas. So we sally forth into a kind of wilderness, an economic fairyland. We are myth busters in a world where people crave myths more than reality. Why do they so readily embrace untruth? Primarily because the immediate costs of doing so are so low and the psychic benefits are so high.