The Japanese team overwhelmed Sweden in their semi-final 48-0.
Sweden gained automatic qualification for the tournament as winner of the 2005 European Championships.
Japan and the United States will play the final Sunday, while Sweden will play
Germany for the bronze on Saturday.
The US team, taking part in the competition for the first time, were 33-7
winners in the semi-final over Germany, who held the Americans to 16-7 in the
first half before letting down their guard.
Japan won the first two American Football World Cups held in 1999 and 2003.
But the US did not take part in the previous competitions.