“That in fiscal year 2004 and thereafter, funds for bridge alteration projects conducted pursuant to the Act of June 21, 1940 (33 U.S.C. 511 et seq.) shall be available for such projects only to the extent that the steel, iron, and manufactured products used in such projects are produced in the United States, unless contrary to law or international agreement, or unless the Commandant of the Coast Guard determines such action to be inconsistent with the public interest or the cost unreasonable.”