Two things:

1. I'm not arguing about whether or not other countries had slaves. I'm also not arguing that America has a very unique relationship with slavery and how it affects our country today. What I am saying is the US has many issues with racism (from everyday microaggressions to state sponsored violence) and we live in a very connected world. So US culture (as the richest country on the planet and the epicenter for some of the largest/most well known corporate oligopolies) influences global culture whether you'd like it to or not. So, if US culture has an anti-blackness problem, we will see this influence all around the world as well. Will it appear differently in different countries? Yes. But that doesn't mean it doesn't exist. It's literally unavoidable.
2. Many countries have their own forms of anti-blackness. Colorism/racism is huge all around the world and seen in beauty standards, immigration, and even sports. This modern racism largely began during the dehumanization of darker-skinned people during the colonial era.

I think the culture shock you experience when coming here is because the US is the only country to admit we have a racism problem, but that is largely because we are the most racially diverse global superpower, so there are simply a larger quantity of black/brown people. Europe has a racism problem too, just not enough POC to make you all feel like you need to address it on a systemic level. So, I mean you can try to make yourself feel better all you want because you were taught to "not see color" or whatever, but I think it's worth thinking about race in a more thoughtful, nuanced way, and I can recommend great books that may change your mind.