You seem to have made a connection between nationalism and being furious about other people. I respectfully disagree that there is a necessary relationship there.
I have no ill will against other people. I would like people who share my culture to govern me, and I would not like people of my culture governing people of a different culture. They can govern themselves and we can govern ourselves. We can share ideas, trade, sport, etc., But multiculturalism within borders is an inevitable failure and globalism is an inevitable failure
Drawing a line primarily along cultural lines means ignoring or downplaying all of the other lines that other people might find similarly important or more so.
Why would I bias my decisions about people over other people just because they grew up within a few hundred kilometres of me? Why would I prefer helping a bunch of deadbeats from my own country over a bunch of promising bright people from halfway across the world? Because they'll stand up for me in return?
Because it's always one team against another? Fuck teams. There are my immediate friends, and outside of that I'll fight only for principles, not arbitrary teams. Everyone's a different person in their own right. Everyone deserves to be treated as who they are, not where they're from. (Cue Backstreet Boys.)
As an example, I stand for freedom of speech, in the form of a diverse, largely independent set of publishers and authors that allows me to make up my own mind by exposing me to different viewpoints. Many Western countries have a better track record at this than authoritarian countries. But this doesn't mean that I'm on Team "The West" - if my country drops this value, I'd rather drop my country than my values.
If my country thinks that skin color or wardrobe of a person is more important than what that person is saying, I'd rather drop my country than team up against that person.
If my country decides that Islamic Law or autocratic dictatorship is a better form of government than democracy, I'd rather drop my country than abandon my principles.
It's great to be in a shared space where you agree with everyone. The question is, when you eventually disagree (because you don't get to choose what your neighbors think, and because nationalism is just a proxy for actual values), then are you going to follow your principles, or do you let your nation and culture dictate what your principles should be?
I think the problem that you are going to run in to is that culture and nations as a proxy for principles works pretty well since those things are highly correlated. Unless you have a strong civic identity that aggressively assimilates and ensures respect of those civic norms, you have an inevitable clash that just becomes a question of scale.
>If my country decides that Islamic Law or autocratic dictatorship is a better form of government than democracy, I'd rather drop my country than abandon my principles.
In your hypothetical, how exactly would this situation come about? You should be able to venture a guess.
When did this ever happen in history? People diverge all the time, that's how we have so many cultures.
Lightly categorized in so called country's?
I am saying this as a person, who likes the science fiction level of species level organization ( vs geographical nation-state ), where we pay with universal credits and basically have few of the issues inherited from the olden days of 2021.
But I dream.
If corona told us anything, then this is probably not true anymore.
Before nationalism, most European states were monarchies "answerable by God". Now it's dominated by countries with a single people/single language/single religion. Minority rights are important, but a minority should never be in charge of the majority as it was under the Austrian Empire for example (a.k.a as the Jail of Nations).
It's sad that reactionaries are trying to undo this and slowly turn the EU into another Austria, which will inevitably be dominated by the Germans and French.
