The Securing American Firms and Expertise in Services Act directs the Secretary of Defense to revise acquisition regulations within 180 days to give preference to United States companies for professional services contracts, consistent with national security interests. A "United States company" is defined as a U.S.-organized business with its principal place of business in the U.S. and no foreign ownership or control, covering services like engineering and financial consulting. The Secretary of Defense may waive this preference if it impedes urgent operational requirements or if no U.S. company can fulfill the contract timely or cost-effectively, with such waivers requiring written justification and notification to congressional defense committees.