Rebuilding American Manufacturing Act of 2012 - Amends the Internal Revenue Code to allow taxpayers engaged in domestic manufacturing in the United States a tax deduction equal to 43% of the lesser of their domestic manufacturing income or their taxable income for the taxable year (thus effectively reducing their income tax rate from 35% to approximately 20%). Limits the amount of such deduction to 25% of such taxpayer's qualifying domestic investment (defined as the sum of the taxpayer's W-2 wages and certain allowable tax deductions, excluding any amounts not properly allocable to the taxpayer's domestic manufacturing gross receipts).