Biometric Identification Transnational Migration Alert Program Authorization Act of 2019 This bill provides statutory authority for the Department of Homeland Security (DHS) Biometric Identification Transnational Migration Alert Program (BITMAP). The program was established to address and reduce national security, border security, and terrorist threats before such threats reach the international border of the United States. DHS must ensure that any biometric and biographic identification data of U.S. citizens that is captured by BITMAP operations is expunged from all databases to which such data was uploaded, unless such data is retained for specific law enforcement or intelligence purposes. The Government Accountability Office shall conduct an audit that analyzes the effectiveness of BITMAP operations.