This bill approves an amendment to the existing U.S.-United Kingdom nuclear cooperation agreement for mutual defense purposes that was signed in July 2024. The legislation allows the amendment to take effect immediately upon passage, bypassing the normal congressional review process that typically requires a waiting period before such agreements can be implemented. The amendment remains subject to all existing laws governing atomic energy and nuclear cooperation, including the Atomic Energy Act of 1954. The bill affects the two countries' ability to share nuclear technology and information for defense-related purposes. No specific funding amounts or detailed implementation timelines are outlined in the legislation.