Nation Building Here at Home Act of 2012 - Directs the Secretary of Transportation (DOT) to establish a transformational infrastructure competitive grant program to award grants to state and local governments, transit agencies, and port authorities for certain public transportation projects (including water infrastructure projects) with potential to significantly impact a metropolitan area, a region, or all of the United States.
Specifies the federal share of project costs at 100%.
Requires the iron, steel, and manufactured goods used in projects funded under this Act to have been produced in the United States, except in specified circumstances.
Directs the Secretary of the Treasury to establish a Nation Building Here at Home Financing Initiative.