I concur with that. Obviously today there is much more exposure to the rest of the world through many channels (travel made easy, tech and social media, etc).
History contributed a lot to it. I will, however, not reduce this to just the US. I was in Europe before I moved to the US, and Europe is just more refined about expressing racism.
Though I live in one of the seemingly most progressive areas of the country, seldom a day goes by that you don't see some aspect of racism in society. Given there is a good mix of different cultures here and the fact that English is the language of the US, most people from other countries are naturally more attracted to an English speaking country. Hence I have always found that racism seemed more glaringly prevalent in such countries (like the US, UK, Australia), but its undertones are clearly there in non-English speaking countries, too, like Germany, France.