Actually I believe the argument was that fundamentalism was a major source of violence. No judgment whether it was for good or evil. Also that it was obviously not the only source of violence in the world.

Anyways.

Nationalism has also been a source of violence, I agree. Look at the french revolutions, a real rise of nationalism in Europe. Beheadings o-plenty, and that was against themselves. Nazis used a sense of nationalism and racism to justify attempting to conquer Europe. The U.S. and manifest destiny...

Nations are based on the entirely on fantasies that have no connection to any empirical reality.

Nations are based on abstract concepts. A huge portion of things in our lives are. That doesn't mean they have 'no connection to reality' or are a 'fantasy', a fundamental thing that makes us human is the ability to understand and create complex ideas and use these ideas to abstract real world things in ways that let us talk about and communicate to others huge volumes of information at a time.

The rest of your stuff: no constitution is valid? Where are you going with this?

I'm guessing you're attempting satire of something or other, but you might have been better off to just come out and say the comparison you're trying to make.