I think it's maps very well onto the "Western" world. Could you describe the ways in which it doesn't? Core countries are typically those that historically benefitted the most from colonialism, and parlayed that advantage into today's complex global trade and markets.
Spain is considered core as it did that more successfully than Portugal, who is considered semi-peripheral. It also helps explain some of the racial things you're talking about, like how Japan is part of the imperial core both from its own imperial exploits and from it's relationship with the us in the postwar period. Much of Japan's racial expectation in the otherwise white western world as the model minority is a cultural effect downstream of their important place in the flow of surplus value from the imperial periphery to the core
This is the best summary I think. For my comments on the thread here (and maybe others) it might just be a miscommunication issue though. Of course latam has it's own exploitative history, and myself and others often exclude much of latam from "the west" on the basis of world systems analysis as periphery nations. But I think the point is this shouldn't exempt latam countries or political movements from criticism. It's a good post imo