Maintaining United States National Security Interests in Europe Act This bill requires the President to take certain actions before reducing the overall presence of the Armed Forces in Europe, such as by withdrawing Armed Forces or Department of Defense personnel or closing a U.S. military base in Europe. The bill also contains other related provisions. Generally, no later than 180 days before taking an action to reduce the U.S. presence in Europe, the President shall report to Congress (1) a justification for the action, (2) the scope and description of the reduction, (3) an explanation of the action's national security benefit, and (4) a plan to offset the reduction in conventional deterrence against Russian aggression stemming from the action. This requirement shall not apply if (1) a country hosting the U.S. forces requests the reduction in writing, or (2) Congress passes a joint resolution or act expressly authorizing the reduction. The President shall report to Congress a detailed account of the decisionmaking process behind the decision to withdraw Armed Forces members from Germany that was announced on June 15, 2020.