hork said: "Those two articles you linked to are about the U.S. only. Does every culture in the world have a prejudice against darker skin?"
I can't speak for every country, but in short
Racism looks different in different countries, as different countries have different racial histories and even different conceptions of race. I'll toss out two examples; Canada has a very contentious history with indigenous peoples, and there is a ton of racism directed towards them. I also think of a friend who is a second generation Chinese immigrant, who told me stories about how when he dated a Vietnamese girl, his extended family was very unhappy because of her race and felt she was not 'good enough' for him. (Thankfully his immediate family was happy for him). Or look at different conceptions of whiteness in Europe vs the USA historically, especially eastern europe.
For Japan I'll refer you to the Japanese themselves: https://www.japantimes.co.jp/opinion/2018/06/03/commentary/japan-commentary/face-reality-racism-japan/
"Japanese have an implicit bias against blacks, concluding that “Japanese participants showed an implicit preference for ‘white people’ over ‘black people.’ ”
That being said, the USA is a dominant force in the world at large. I don't live in the USA, but most of my media comes from the USA. The songs I listen to, the movies I watch, the books I read. That affects you. Google "the danger of a single story" for an incredible example of that.
In addition, the USA (and other western countries, but really, the USA) deliberately meddles with politics in other countries, including racial politics. Look at Apartheid in South Africa
Racism looks different in other countries sometimes, but there is still racism, and the united states has such a disproportionate affect on other countries at this point in time that I think an analysis of race in the USA will always be relevant.