Nationalism is responsible for some of the most technologically advanced societies in recent history (the U.S. and Great Britain). Nationalism is a powerful force for motivating people across class divisions to work together to build things.
Humans have a limited capacity to empathize with other people. Modern communications technologies and the worldwide export of Western culture has increased that capacity, but it's easy to overestimate how much we can really change in that regard. See, e.g., lofty ideals of pan-European identity being crushed by cold, hard, economic reality.
I think you have too little faith in the future. Heck, even if you're right, shouldn't we at least strive toward the unattainable goal of a global "tribe"?
