Not to split hairs but I don’t think there’s any “amerikkka” in settlers. Sakai uses “Amerika” and yea I believe he borrowed it from other groups. My memory is a little fuzzy on the specifics, another comrade may know better, but I think it came from some black or afro nationalist orgs or other things like that. It definitely predates settlers
Amerika was fist used in the 1960s, to liken the United States to Nazi Germany, as it's the German spelling of America.
Amerikkka was an evolution of that popularised by music, magazines and books as far as I know. I know NWA and Ice Cube used it a lot in their music and promotional materials.
Lots of Mao's writing is very direct and clarifying while simultaneously having a particular feel/cadence to it through virtue of translation. Couple that with the insular dogmatism of many white "maoists" in the US, and you get a special flavor of English.