> How do you fight a war on "structural racism"?
You are either seeing something I can't see or you are implying that it is not possible to fight against racism, which is indeed structural. (Except in the context of propaganda, I don't see the need for the adjective, since the people who can see its connection with the mode of production will note that it is structural and those who don't will fight against the symptoms, which is a starting point.)
In either case, I'd like to read a clear statement on what you mean specifically.
Now, to answer the question -- although it seems to me that this is not what you really mean to question:
Different people in different contexts wage this war in different ways. White people interested in helping can start by supporting the struggles of Black people in their various settings (yes, including OWS). But the struggle against racism is *led* by those oppressed by racism. It's the fight for international equality as it was waged by Africans, Caribbeans, and Blacks in the U.S., Europe, and wherever they happen to be. In the U.S., it is the fight against the prison industrial system, for jobs, for public schools, for public health care, better and more public housing, affirmative-action government spending, etc. as it is concretely led by Black people.
Re. OWS and race: In my (very narrow, limited) experience with OWS, people are incredibly mindful of the disadvantageous social conditions of Black people, and they are making a genuine conscious effort to cooperate with Black people in good faith. On the other hand, the Black people who are participating appear to be very focused on the advance of OWS, rather than emphasizing racial differences within the movement. And I believe this is the way it is supposed to work out -- radical Whites are supposed to insist on the matter of racial equality and Blacks are supposed to focus on the aspects of the movement that advance the agenda of working people in general.