Promoting United States International Leadership in 5G Act of 2021 This bill requires actions to increase U.S. influence in international organizations that develop and set standards for wireless telecommunications, such as fifth-generation (5G) technology, and to address the role of China's government in such standards-setting organizations. (Such organizations, with the involvement of stakeholders such as equipment manufacturers, develop and set standards for certain technologies to ensure interoperability between different companies' products.) The President must establish an interagency working group to work with allies and international partners to increase and align their engagement in standards-setting organizations, such as the International Telecommunication Union, that address standards and issues pertaining to communications networks, including 5G technology. The Department of State must, in coordination with the working group, develop and implement a strategy to work with allies and partners and monitor efforts by China's government (and affiliated entities) to control or influence such organizations. The working group must provide a briefing to Congress on (1) a strategy for diplomatic engagement with allies and partners to cooperate on addressing security risks in 5G and future generation mobile telecommunications systems, and (2) the presence and activities of China's government in international standards-setting organizations.