Now, in many circles, people have adopted a guilt ridden opposite of nationalism. People genuinely believe that helping a countryman is an ethical dilemma so long as there is someone worse off.
* I don't think many people are so extreme as the 'opposite of nationalism'. In fact, I think that nationalism (or more broadly, the basic tribalistic instinct) has such an natural, powerful pull on people that it will never need to be encouraged.
* I think it's great that many people moderate their nationalistic instincts now with reason and compassion. Not only did millions get slaughtered for the nation (or the race, or whatever), but they murdered millions more. The moderation of 'tribalism' with liberal ideas might be one of the most important changes in humanity's history.
* Unfortunately, I see nationalism and other tribalistic ideas as rapidly spreading again. It's promoted by state school boards in Texas and Oklahoma; many national leaders push it, for example in Russia, China, Japan, and South Korea (off the top of my head). Outright religious 'tribalism' is rampant in Europe and, to a degree, the U.S. The EU's unity is under serious strain, Scotland almost succeeded from the UK, and parts of Spain and other countries are discussing the same. Nobody stands up for the value of the liberal ideas and institutions that kept the peace since WWII.
Arguably, there are two kinds of political movements (and leaders), those that bring people together, and those that play on tribalistic instincts and divide them. One kind has much better results for humanity.
There are two kinds of political movements (and leaders), those, like narcissists, forcefully change others into themselves, remove differences between peoples, demolish language and culture, and those that remain resolute in being non-interfering of others, even while being interfered with, allowing other humans to live according to their humanity.
In Firefly - you would be part of the alliance. In Star Wars - you would be part of the empire. In the People's Republic of China, you would be part of the CCCP. In the U.S. you would be part of the Federal government. In Europe you would be part of the Troika.
And I accept that is your nature.
The most prosperous, safest and most peaceful countries in the history of the world, by a long shot, are the freest.
I don't mean to say that there's any reason to think you're lying here, but I think it's worth pointing out that the identical argument fails very badly in different circumstances.
That's the 'tribalism' I'm talking about. People can divide into 'us and them' over nations or states or race or wealth or whatever. I agree with the downsides and your example.
But it's not intractable. We're not living in family units in caves; we've formed societies, nations, companies, bowling leagues, etc. Humans are naturally social, cooperative, even herd-like organisms and they do work together, organize, and build inclusive social structures.
The very divided states of 1776 did form the United States of today, though it took a little work. The Germanic states formed Germany. Europe did make peace and form the EU. Think of the notion of "white" in the U.S.: There used to be violent, hateful divisions between Protestants, Catholics, and Jews; between Italians, Irish and Germans (and more); it was a big deal when JFK was elected in 1960 that he was Catholic. Now that all would be absurd; those people are just "white" (and the division is with black and Hispanic peopl, and with Muslims). We had segregation, and now we elected a black President (though we still have a ways to go.) LGBTQ people are now widely accepted as just people.
Pretty sure Europe, the Middle-East, Asia and Russia will all still be here in some form in a few generations.