National Domestic Violence Prevention Action Plan Act of 2021 This bill establishes an interagency steering committee within the Department of Health and Human Services (HHS) to expand, intensify, and coordinate federal and nonfederal actions to prevent domestic violence. HHS may include nonfederal subject matter experts if necessary to carry out the committee's activities. Specifically, the committee must develop an action plan to guide a whole-of-government, goal-oriented approach to domestic violence prevention. The committee must include, as part of the plan, a national media campaign to engage with the public on matters concerning domestic violence prevention.