Countering Iran's Destabilizing Activities Act of 2017 This bill directs the Departments of State, Defense, and Treasury and the Director of National Intelligence to submit a strategy every two years for deterring conventional and asymmetric Iranian activities that threaten the United States and key allies in the Middle East, North Africa, and beyond. The President shall impose asset blocking and U.S. exclusion sanctions against any person that materially contributes to: (1) Iran's ballistic missile or weapons of mass destruction programs, or (2) the sale or transfer to Iran of specified military equipment or the provision of related technical or financial assistance. The President shall impose against Iran's Islamic Revolutionary Guard Corps and affiliated foreign persons sanctions with respect to blocking property of, and prohibiting transactions with, foreign persons who commit or support terrorism. The President may impose asset blocking sanctions against any person identified by the State Department as responsible for extrajudicial killings, torture, or other gross violations of internationally recognized human rights committed against certain individuals in Iran. The bill requires specified existing sanctions against persons for materially contributing to Iran's ballistic missile program or for supporting Iran's acts of international terrorism to continue until 90 days after the President certifies that such activities ceased during the immediately preceding three-month period. The bill exempts certain humanitarian and national security activities from sanctions. The President may temporarily waive the imposition or continuation of sanctions under specified circumstances. The bill sets forth reporting requirements with respect to: (1) persons contributing to Iran's ballistic missile program, (2) U.S.-European Union sanctions coordination, (3) U.S. citizens detained by Iran, and (4) each use of the waiver authority.