American Timber Supply and Manufacturing Incentives Act

American Timber Supply and Manufacturing Incentives Act - Amends the Internal Revenue Code to provide taxpayers a deduction from gross income for qualified timber gain as an investment incentive. Allows such deduction in computing adjusted gross income. Provides for applying passive loss limitations to timber activities. Provides that export property eligible for certain tax incentives does not include any unprocessed softwood timber for purposes of: (1) taxation of foreign sales corporations (FSCs); and (2) taxation of domestic international sales corporations (DISCs). Requires any income from the sale of such unprocessed timber which was cut from an area in the United States to be sourced in the United States. Excludes such income from rules under which: (1) gains, profits, and income involving inventory property purchased in the United States but sold or exchanged elsewhere may be sourced foreign; and (2) income derived from the manufacture of products in the United States and their sale elsewhere may be treated as having a divided source. Repeals the deferral from income of the controlled foreign corporation from sales or milling (outside the United States) of unprocessed softwood timber to the extent that any controlled foreign corporation is owned by ten percent or more U.S. shareholders.