To me it's really because they have broken that promise. Governments take advantage of that cohesion. It's not really because of the transactionality to my benefit but just because what they stand for is a net negative for society and the world.

Consider the military. Few wars are actually worth giving one's life for. Since 1945 basically none. If the Communists had won in Vietnam nothing would have happened to America. Iraq was based on false pretenses, Afghanistan accomplished absolutely nothing. My own country was part of some of these misguided adventures and has some of its own wars where it definitely was the evil aggressor.

Or think of the Nazis who exploited the very concept of this nationalism to destroy half the world.

So no. I do think it helps social cohesion but when a state is using that cohesion for evil it does not deserve to be followed.

I think we should outgrow this petty follow the leader attitude and think for ourselves.