People was shockingly racist in 1900 to our modern standards, so just take away the things that made them think twice.
1) Japan fails to modernize as much as China. The idea that Asians are only good at copying Europeans but never enough to reach their level sticks.
2) Shorter and more reduced WW1, resulting in German victory:
::Non-European countries never join in (thus no presence of Japan, Liberia, Siam, China, Brazil, USA, etc as equals at the peace talks).
::British and French colonial troops don't prove to be as good soldiers as Europeans, but are seen as mere cannon fodder easy to tear apart by ''by superior Aryan men'' *cough*armed with machine guns*cough*. (possible knock on effect, imagine the domino-downfall of French lines that lead to a German victory actually starts as mutinies among discontented Senegalese or North African recruits, leading to an increase of racism in defeated France).
::No Nazis, thus no shame for their crimes and no apparent reason to drop the traditional racism altogether.
::No WW2 either (though there might be one or two limited European conflicts more) so no non-white heroes again from the USA, China, Free France etc nor even more non-western countries joining "the good guys" to fight together.
3) No post-wars inmmigration from the colonies, but increased European inmmigration to them instead.