People can have more than one cultural background, and American "black culture" is the common cultural heritage around the experience of being black in America, which has a lot of broad commonalities regardless of where in the country you are, and also locale-specific subcultures (e.g. west coast vs east coast vs deep south).
Like the whole point of Fresh Prince of Bel-Air was that Will Smith and his uncle's family had very different subcultural contexts (although their divide was less "Nigeria vs Jamaica" and more a class divide), but also shared the broader experience of being black in America.
They don't necessarily. Not speaking for the BlackOakTV folks here but I don't think this is trying to target all black people. The US is somewhat unique in having a large population that was ripped from their respective home countries and forced to create their own shared culture under the thumb of slavery. Someone that immigrated from Nigeria in the last decade doesn't have that same experience.
Unique?
"Between 1502 and 1866, of the 11.2 million Africans taken, only 388,000 arrived in North America, while the rest went to Brazil, the European colonies in the Caribbean and Spanish territories in Central and South America, in that order"
"The melatonin in their skin" explicitly shaped many aspects of law, society, and culture in the US up until the 60s, which is still in living memory, so I don't think it's that surprising that there would still be measurable differences in culture and media interests.
Think about how much your parents' lives and the stories they told you are reflected in your present-day values and interests.
I see it regularly today, as African-Americans and many other people commonly say. We can recall that overt racism is practiced in certain political groups which have expanded in popularity. Research shows that racist attacks have greatly increased over the last few years. Regarding the law, many of the laws that existed before the Voting Rights Act have been recently reinstated since the Supreme Court invalidated key parts of the Act and banned federal courts from addressing many state voting issues.
It's also not rare anymore in my personal experience, as it was before 2016. In the last month a white person told me that people with black skin were 'biologically different', which accounted for economic inequality. Over the weekend another told me, highly ironically, that 'minorities' were more prone to disinformation than white people, and that was the cause of problem of disinformation on the Internet. (For the record, I disagreed with both as effectively as I could - you can't tacitly approve.)
A significant cause of discrimination is that its impact and presence is overlooked by people who aren't affected by it. Racism doesn't affect me (directly), so it's not hard to say it's minimal.
I intentionally avoided discussing modern politics in order to make a stronger (albeit more limited) argument, by emphasizing explicit legal discrimination. Even if someone doesn't believe in systemic racism, it's not a point of debate that black people alive today were explicitly persecuted under the law based on the color of their skin.
I understand what you are doing now and that used to be my approach. Now, I feel that it just allows the denialist rhetoric to perpetuate. I'm not even going to call it a myth because it's such obvious nonsense, I believe even to the people that say it - it's just push-back, a tactic.
There's the further concept that due to systemic racism, Jamaican and Nigerian culture will blend into the larger black culture than the larger US culture. And the Nigerian and the Jamaican will experience a similar American experience, very different from what an Irish or German white person would.
It's really self-centered when we use "black" to mean "African American". It's strange when it goes the other way. You'll hear some Americans call Idris Elba an African-American.
I'm all for dropping the term African American, unless it's referring to a recent immigrant. It's a misnomer from the past, that for some reason people consider PC.
Based on their skin color, they are treated the same way by much of society. They are often compelled, for safety and for just day-to-day peace from racism, to live in the same neighborhoods, go to the same schools, eat at the same restaurants, visit the same websites (where they don't have to read racist comments), play the same online games (ditto), etc. - heck, you can't even watch porn without encountering endless racist portrayals based on skin color. So people with 'black' skin have many common experiences.
Also, market segments don't have to be perfectly defined. We can always find flaws - no two people are alike; no one person is exactly alike from one day to the next.
Both are referred to as "black" (or worse), anywhere they go in the world, and both suffer the effects, prejudice and discrimination of racism - anywhere they go in the world.
Another fan fact - your hypothetical Jamaican and Nigerian, are the most likely to type "How does country X treat black people" before deciding whether to visit a country on holiday - something very few other people (if any) do - so there is a lot that binds the Jamaican and Nigerian together - the nonsensical (but very problematic) notion of "race".
HTH