My guess is that its the large amount of nationalism Europe has traditionally had. Politicians and leaders have always blamed internal problems on outsiders going back to the dawn of time, while this happens everywhere it is much easier to do so when you were at total war with those outsiders n years ago.<p>The Americas are in a unique situation because the dominant power, the US, contains large percentages of citizens with South American, Mexican, Canadian, and Asian, heritage. You still get violence and hate speech, but the strife between them is relatively short lived even when considering the likes of Japan, Vietnam, and China.<p>Then you have the religious and cultural differences between western and middle eastern values. I think this transcends everything as you see the same distaste of middle-easterners in both Europe and the United States.