"okay for black people form an identity behind their race"

Probably because they get referred to as black and get discriminated against due to their physical appearance regardless of their actual heritage or where they're from? It's not so much a choice as something that they get constantly reminded about.

Anecdotally speaking, there are Black communities, but I've never seen a "white" community (aside from white supremacist type groups)- just communities of nationalities or ethnicity. I grew up in Romanian communities and none of us ever used "white" as an identity.

Not everything is about you or me.