I don't think anyone is arguing that on a global scale though colonial/Western powers did decimate Africa and continue to actively prevent its advancement via neocolonialism there.

But if we're talking about American history then we need to be transparent about the fact that this was an apartheid state until about half a century ago and the consequences of that reverberate to the present day.

You probably mean well, but this rings of "all lives matter." There's nothing wrong with pointing out injustice and oppression, in isolation. The issue lies in using it as a rebuttal to the suffering of others. "The Irish were enslaved" is fine, but "white people were slaves, too," is minimizing the vast industry of oppression that was the slave trade.

No one is claiming a patent on suffering, but you are minimizing theirs. You can acknowledge suffering without trying to draw comparisons, and especially without the strawman argument. The phrase "black people don't own the patent on suffering, sorry" rings of resentment and snark, and isn't at all representative of most black people's view of human suffering. Oppressed people support each other and prop each other up. We aren't measuring each other's suffering or keeping score. Some of my greatest allies are people that don't share my own personal struggle, but relate with their own, and I likewise support them (I am a queer white woman).