Losurdo really drives home that white/western supremacy has been a global project that's gone through many phases, not just limited to one country.
The word untermensch for example, comes from lothrop stoddard, a US white supremacist and eugenicist who greatly inspired the nazis. They also took lebensraum from manifest destiny, and openly wanted to emulate what the US did to its native population, in eastern europe.
After the nazis broke the rules and attacked westward and started western infighting by attacking britain and france, then lost in ww2, the US took up the mantle of the west's leading country who would keep the non-white populations of the world in check, by bombing anyone who dared to challenge colonialism or neo-colonialism, or impede their control of resources and prevent the spice from flowing.