Advancing Cybersecurity Diagnostics and Mitigation Act This bill requires the Department of Homeland Security (DHS) to establish a program to assist agencies with continuously diagnosing and mitigating cyber threats and vulnerabilities. Pursuant to this program, DHS shall (1) develop the capability to collect, analyze, and visualize information relating to security data and cybersecurity risks at agencies; (2) make program capabilities available for use by civilian agencies, states, and local governments; (3) assist such entities in setting information security priorities and assessing and managing cybersecurity risks; and (4) develop policies and procedures for reporting systemic risks and potential incidents. DHS must also regularly deploy new technologies to improve the program. In addition, the Government Accountability Office must report on the potential impacts and benefits of replacing existing reporting requirements under the federal information policy with periodical real-time data provided by the program.