I think you've nailed it. Many people act as though it's an "either/or" proposition. Instead, it's really a "both/also" scenario.

Systemic racism, as you've outlined, is when institutions and governmentally-supported systems ravage the lives of BIPOC Americans. This has been happening for centuries, and many are unfamiliar (or uncomfortable) talking about it.

Social Racism and Cultural Racism are when individuals (or groups) try to leverage racial prejudice, turning it from a passive attitude or belief (prejudice) into a tangible or behavioral action (bigotry, and, eventually, discrimination).

The problem is that so many leftist academics in their ivory towers want to unilaterally redefine "racism" per se as ONLY pertaining to the problems known as systemic racism...while relegating all other racially-motivated acts to the definition of "prejudice."

They don't seem to realize that multiple things can be true at the same time. Or they're just banking on "uneducated" Americans being too stupid to tell the difference. We're not.