[wcoenen]

Actually, it is the Department of Treasury that prints and mints new money. This entity is part of the government, and also manages tax collection etc.

Though you are right that the U.S. government can't print & spend directly. The printed money has to be brought into circulation by the Federal Reserve, which lends it out at the Fed rate. Then again, the Federal Reserve's profits go back to the Treasury so the government can in practice borrow the printed money from the Fed without interest.