China Financial Threat Mitigation Act of 2021 This bill requires U.S. representatives to certain international bodies to advocate for increased international cooperation to mitigate threats caused by the governance, opacity, or instability of financial intermediation in China. (Generally, financial intermediaries provide services, such as accounting and underwriting services, that facilitate financial transactions.) Specifically, this requirement applies to U.S. representatives to the International Monetary Fund, the Group of 20 (G20), and the Financial Stability Board (a technical body established by the G20 to coordinate the group's agenda). The bill also requires the Financial Stability Oversight Council within the Department of the Treasury to report annually to Congress on such threats.