How important is the Statement of Contributions to Diversity in applications for faculty positions?
If you submit a strong statement of contribution to diversity, it will help your application in the sense that if you are clearly qualified for the job, this statement would be a plus and would get people excited about your application.  On the other hand, if there are reservations as to whether you are really qualified for the job, in terms of academic merit, teaching experience -- basic stuff -- then a strong diversity stance will not help you.

If you have no previous or well thought out contributions to diversity to speak of, then submitting an anemic diversity statement might hurt you more than not submitting one at all would.

If you are someone who has never given it much thought, then I would advise you not to submit a statement for this particular application; but at the same time, I would encourage you to start doing some thinking about the special challenges diverse students can face getting started, continuing with, and finishing their studies, and what you could contribute to lessening the difficulties.