I believe the German spelling for a lot of things that - in English have the letter ‘c’ in it - use the letter ‘K.’ For example, America and Africa is Amerika and Afrika. The Germans also use K’s in a lot of their own words (Freikorps). And Germany is associated with white fascism and Nazism which also coincides with the KKK, which historically used vocabulary with Ks in it (Klan, Koran, made up words).

I don’t know when it became popularly used as a pejorative against the west, but the most recent example I can think of is Settlers by J. Sakai. However, I’ve seen non Marxist/left black supremacists also use the K variant of spelling so it’s not exclusive to anyone.

In essence, it’s comparing America (and any other western country with a C/K in its name) to the KKK as well as Nazi Germany.