It is in fact not difficult to explain carceral inequality through the prism of white supremacy, as "whiteness" is a fluid concept largely defined in specific opposition to "black" people; historically, it's adapted as needed to embrace formerly "non-white" people (the Irish, Italians, Jewish people) in solidarity against encroaching black people (for instance, during the Great Migration).

A useful thing to keep in mind is that "black", as in "African American", actually is a sort of synthesized ethnicity (their original cultures having been stripped from them in the Trans-Atlantic Slave Trade)... but "white" is not. There are Irish people and there are Slavic people and there are Sicilian people, and their cultures are not in fact all that similar. "White" just means what it needs to mean.

All you need to add to your mental model of "white" and "black" to fit low Asian American incarceration into it is the idea that Asians will soon attain "honorary white" status. That's not a message board concept; the transition of Asians from "model minority" to "white people" is much discussed in the real world as well.