I think limiting the word racism to mean 'racial prejudice plus power' is problematic.
There are circumstances in which this choice can lead to black people suffering racially-motivated injustices that may not qualify as racism if this more specific meaning is adopted.
A startling assertion, I know. Let me try to justify it through examples.
The vast majority of people in the South African cabinet are black - which is as it should be given the demographic of the country. Slowly a more equal society is emerging there.
Suppose that, against this backdrop, a black person in South Africa is treated badly by a white person, simply because they are black. There is a danger that, with residual inequalities fading away, it will become harder and harder to justify calling this racism, given that a person can only be racist, by the more limited definition, if they share a racial heritage with those who set the agenda at the highest levels of office.
Nevertheless, I would argue that it is, and always will be, racism, white-against-black racism, simply because it is discrimination against another person on the grounds of race, regardless of the balance of power at society level at any given time.
Put simply, racism does exist at an individual level. Moreover, there are always smaller communities within society at large in which the overarching racial power hierarchy is flipped. Which grouping then to choose as significant?
Another example would be the grooming gangs in the UK mentioned earlier in this thread, the men being mainly - but not exclusively - of Pakistani origin. The majority of victims have been white girls but girls of African heritage have also been targeted and subjected to abuse. Clearly there is misogyny in evidence here but also, I would argue, racism. From their own words, the men involved showed that they did not respect girls who came from ethnic backgrounds other than their own. (I should add that these men have been roundly condemned by people within their own ethnic communities.)
It would be wrong to say that the black girls who suffered at the hands of these men were not victims of racism, simply because the men were mainly non-white. And it would be wrong to say that the white girls who suffered were not victims of racism because they happen to share a heritage with the privileged white majority.
I hope these scenarios might highlight some of the complexities arising from restricting the use of the word racism. In my opinion, this isn’t ‘whataboutery’ and I hope, and trust, that taking time to examine semantics does not detract from the more pressing and heartbreaking situation in the States right now.
We need to keep language flexible to allow all sorts of complicated circumstances to be described, and not to wipe out the possibility of even thinking about certain human experiences by ring fencing the language that would naturally encapsulate those experiences.
If languages becomes impoverished and circumscribed, thoughts are also impoverished and circumscribed.
In the words of George Orwell:
Don't you see that the whole aim of Newspeak is to narrow the range of thought? In the end we shall make thought-crime literally impossible, because there will be no words in which to express it. Every concept that can ever be needed will be expressed by exactly one word, with its meaning rigidly defined and all its subsidiary meanings rubbed out and forgotten. . . . The process will still be continuing long after you and I are dead. Every year fewer and fewer words, and the range of consciousness always a little smaller.