[nazgul17]

I disagree. Caring for "your" people is very much part of human nature. Where you draw the line can change (examples are blood, race, hometown, city, region, nation, continent, family etc), but "us vs them" it is an overwhelmingly common pattern.

[eeZah7Ux]

As JoeDaDude pointed out tribalism is not nationalism. Most mammals are social creatures and, unsurprisingly, tend to bond with their peers.

The idea that someone that you've never seen or met is "your" people because it has the same letters on a passport is a cultural artifact.

> "us vs them" it is an overwhelmingly common pattern

The fact that is common in various cultures does not imply that it is "human nature", but the opposite.

Prof. Sapolsky research on baboons "group culture" is a good example. There are various lectures from him on youtube.