OK, brass tacks time.
When Europeans first encountered non-Europeans, their technology was about equal, and they accepted each other as equals. Then Europe advanced by leaps and bounds, while many of the others stayed put. Rather understandably, this induced a perception of superiority in Europeans which persists to this day. Why other peoples failed to advance is hard to say definitively. Geology, climate, culture, all kinds of factors were and are in play here. But there it was and there it is.
Why does extreme racism exist more potently and openly in the US than elsewhere? Because the Europeans who colonised America deliberately cut themselves adrift from their roots. Such a society is inherently unstable -you don't replace over 2000 years of history in 200. The only thing holding White America together is fear of the Other. Of the First Nations originally, now of the 'free' Peoples of Colour.
In other words, it's a bloody mess!