The "Cross-Boundary Wildfire Solutions Act" mandates a study by the US Comptroller General to assess existing federal programs and regulations regarding wildfire mitigation across land ownership boundaries. The study will explore potential changes to facilitate federal agencies, state, local, and tribal governments in combating wildfires. It will also evaluate activities under the Healthy Forests Restoration Act of 2003, aiming to enhance their effectiveness. The Comptroller General must submit a report with study results and recommendations for simplifying cross-boundary wildfire mitigation within two years. The bill seeks to identify and address barriers to collaborative wildfire prevention efforts between federal and non-federal landowners.