It’s an issues of having an independent versus interdependent self-schema. The latter arose in western countries as surplus started to allow for individuals to survive without relying on mutual aid. Interdependent selves have fuzzy boundaries between themself and their ingroup when it comes to how they self is defined, with hard boundaries between the ingroup and wider world. The aims and beliefs of the ingroup are not readily distinguished from those of the self. An independent self, by contrast, has clear boundaries that atomise them as an individual and have porous ingroup/outgroup boundaries and multiple ingroup memberships. Of course, this is so all an idealised model — reality is not so readily categorised. I’ve also heavily simplified the independent vs interdependent split.