I think it depends on who the "they" is when you say "they realize."
If the TAST didn't happen, like someone else said, there would generally be less people of African descent in the Americas. But aside from that, colonialization probably would still have had resounding affects regardless. No Africans becoming slaves just means that more lower class "white" people being slaves/indentured servants for longer and likely a more severe genocide of native peoples. Colonialization would still happen in Africa and Asia, to the point where, for example, there are millions, probably billions of adults today who are older than some African countries have had their independence. We would still have racism, but it would be branded different. Maybe certain European people wouldn't be grandfathered into the "white race." Maybe there would be more hate for Asian people and Native Americans. Who knows? Removing the TAST would be removing a massive part in how racism looks like in America aka the USA, but European countries would probably just push those socially detrimental, but economically invaluable ideals more as they went on to colonize the rest of the world.
I mean, it is you. It's literally a part of you. If you want to dissociate from the social ramifications of having a certain skin color, you're well within your rights to do so. But saying it's not you is a very lukewarm take.
I think it depends on where you directing that type of language. In general, you're right. Discrimination and segregation between religious groups in Southeast Asia probably have nothing to do with the slave trade. But you would be wrong if the context is American or even European coded racism. Which is what I think the OP is focusing on.
Anti-blackness does show up socially in many countries that are influenced by America. But as an individual it would make more sense on propping yourself and other black people you know up, and less time stressing yourself out on "not being liked" in other countries.
Yes, they would, but imo, it would only be marginally better. Remember that the slave trade was an economic effort and racism mainly was and is a way to keep "white" people economically above all other people. And that your proximity to that whiteness helps determine your economic standing in the world. Eh, for the most part to be charitable.
I think we all have skeletons, but some of us are born missing a forearm or two.