@MontEthna
I fully agree with someone being the sums fo many different parts rather than just the race part of things.
@Linning, I can see what you mean about being both but relating to a specific culture.
It’s an interesting point because listening to black people in the US, I get the strong feeling that being black and being part of the black culture are two things strongly intertwined and inseparable. So you have people who black but with a ‘pale’ colour (their words) who still feel black - as culturally part of the black community. There seems to be quite a bit of tension around that too with ‘darker’ skin people saying that they still have it harder than the lighter skin people and telling them they can’t call themselves black 
They also don’t seem to have the concept of mixed race (unless I’m mistaken)
I used to live in the US and it’s true that black people (regardless of their shade of blackness/darkness) are very attached to their black identity and culture. In fact while in the US, I too fell a very strong sense of attachment to my black identity and to black culture and it did become a center point of my identity and, in many ways, life there. BUT that’s because race and racial divide is SUCH SUCH a big thing in the US.
I used to live in California so probably the most liberal and multicultural place in the US alongside NYC and it was impossible to detach yourself from your ethnic background, no matter which one you belonged to. You are litterally forced to. Not by society as much as by how the US system works. Every form you ever fill ask you about your ethnic background, treatment of individuals from different ethnic backgrounds are treated differently. African-American people are shot by police, Asian- Americans are being beaten up and killed by fellow citizens, Mexicans and Latinos are treated like dirt under people’s shoes. There is NO other way than to become even more fiercely proud and protective of your culture and identity.
In the US there was NO WAY I could even pretend I was white. I absolutely feared the police, and equally feared vocally racist and agressive white folks. The treatment of black people, the stereotyping of black women, the conditions of life of black kids. It’s impossible to ignore. You simply cannot ignore statistics and it was impossible to deny my African black side when there because things that were happening were too outrageous, too painful, too infuriating, and too unfair for me to hide behind any white identity. In fact in the US I became angry, angry at the white side of me/my family. I became even more aware of the ingrained racism in my (white) family, even more outraged by it, at me for not noticing and not standing up to it for too long and at them for bathing in their white privileges all while denying how harmful their views/actions and lack of actions are.
As a mixed race light skin person I absolutely DO NOT have the same experience as darker black folks. I never have and I never will. Black folks are right in saying a brown girl only knows parts of the struggle. As an half-white woman, I have benefited greatly from white privileges. I have a white mom who can get me out of trouble if need be, I have had access (to a certain extent) to the wealth, education and power of my quite family, I have half the generational trauma of a full-black family, I am lighter skinned and therefore seen as more attractive than darker skin women, I don’t suffer from the same negative stereotype as darker black women, I don’t fear the police the way I would if I was darker (it doesn’t mean that I don’t fear them, but that I know that if my family got involved I would have more chances of it being solved without or with less violence than if my entire family was black) and I don’t suffer racism to the extent someone darker does.
As a light(er)-skin black woman I felt deeply black in America, but I am NOT black. I am brown, and I go through life being treated as such.
Mixed race is a thing in the US but remember that most African-Americans are mixed race, a lot are
more dark-brown than black and most African-American have NO clue of their ancestry due to slavery. The notion of Bi-raciality is therefore way less understood and less inclusive/accepted than in Europe. It’s a problem but it’s also not surprising when you look at the US history.