Evidence indicates that the "race realists" are wrong. When you search for explanatory factors for IQ differences, the best study I know of has an interval for race that includes zero and, more importantly, the confidence interval is only about 2 IQ points (see supplementary data for https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7506587/).

Note that the same study also indicates that most of the factors you mention--which are indistinguishable in this study from genetics of race!--also don't matter to IQ.

Anyway, you don't need to argue this one indirectly by bringing up systemic racism. It's been tested, and the evidence says: no, that does not seem to be how it works. Maybe the "race (un)realists" need to be reminded that facts don't care about their feelings.

(Fiddly technical point about race x variable interactions not being tested and/or lack of mediator variable analysis omitted in the interests of space. tl;dr is that it's not totally locked down statistically, but nonetheless our best evidence is: if it does anything at all, at most it's a very small effect not "almost entirely genetic differences".)