Buy American Improvement Act of 2003 - Amends the Buy American Act to: (1) prohibit Federal agencies from making a determination that it would not be in the public interest to enter into a contract subject to Buy American requirements after a procurement notice for such contract is published; and (2) provide that Buy American requirements shall apply without regard to whether products are acquired for use outside the United States if they are not needed on an urgent basis or if they are acquired on a regular basis (but requires an analysis of the difference in costs of such products from manufacturers inside and outside the United States before a contract is entered).
Requires Federal agencies to: (1) give preference in the procurement process to a company that manufactures the solicited product in the United States if such company's bid is substantially the same as a bid made by a non-U.S. manufacturer or such company is the only company that manufactures the product in the United States; and (2) report annually on agency acquisitions from entities that manufacture products outside the United States.
Prohibits an agency head from making any determination that articles to be procured are not available from domestic sources without conducting a study that determine that domestic production cannot be initiated to meet procurement needs and that a comparable product is not available from a company in the United States.
Defines a product as made "substantially all" from domestic components when the cost of such components exceeds 75 percent.
Requires the Comptroller General to report to Congress with recommendations for defining "unreasonable cost" and "inconsistent with the public interest" for purposes of applying waivers of Buy American requirements.
Prohibits an agency from entering a contract with a foreign entity that involves giving such entity information that would facilitate the manufacture of a dual-use item on the Commerce Control List unless approval has been obtained in accordance with the Export Administration Act of 1979.