Looking at his claim isolated from his evidence is hard to discuss. I think that also came from a TV interview, which is not the ideal forum for him to present evidence.
(When discussing "systemic racism", let's set aside specific racism, which can (and should) be specifically called out and changed.)
To explore systemic racism in more detail, we'd want to look at some measure (not necessarily a single number) of systemic racism. Once we have a way of measuring it (even crudely), we could compare across various races, countries, states, and regions. Importantly, we could compare it within a given race -- if systemic racism varies within a race, then clearly we need to revisit the definition because there are other factors at work. We could also look for other signs that something is awry, like areas that are "systemically racist" against the most politically powerful group.
Dr. Sowell has been performing this kind of research and analysis for decades, and documents it extensively in his many books.
From the quotation above, it seems that he believes that he believes that the term "systemic racism" has no useful definition remaining after this analysis, and that it's being used as propaganda to undermine institutions that stand in the way of political goals.
If you believe that systemic racism is a useful construct that leads to solutions for a better world, then by all means follow where it leads. But please focus on offering alternative policies that lead to good results, and adapt (or revert) those policies if they lead to bad results. Don't just turn it into a never-ending "discussion" that divides people with no solution.