USA had the ideal start with a goal on 8 minutes. Tobin Heath found Alex Morgan on the edge of the box and she was allowed to turn and cross, with Carli Lloyd finding the net with a stooping header in front of Abby Wambach's boot.
Japan came very close to equalising twice, Nahomi Kawasumi's shot blocked almost on the line, Yuki Ogimi's header came back off the bar and she hit the rebound wide off balance.
Japan might well have been awarded a penalty but Heath escaped a handball in the box from a free kick.
Wambach's driven ball into the box bounced awkwardly and Iwashimuzu managed to glance it against her own post - the closest the USA came to a second goal in the first half.
Shinobu Ohno picked out Miyama whose header was turned onto the bar by Hope Solo and then Ohno's strike was wide of the right-hand upright.
Miyama had a free kick early in the second half and Solo hurt defender Rachel Buehler, who had taken a forward down with her but wasn't penalised.
Miho Fukumoto had to palm away Morgan's cross with Wambach lurking dangerously and it was 2-0 on 54 minutes, Carli Lloyd with an unstoppable 20-yard strike on the break.
Ogimi pulled a goal back on 63 minutes after a block on the line from Homare Sawa's shot and a failure to clear the ball. A corner was immediately forced by Japan but Solo claimed well.
Buehler got to a free kick in the six-yard box but Fukumoto blocked it with her feet.
Ogimi went close with a header when meeting Miyama's free kick and there was a scramble to clear the ball after a block in front of Solo from Saki Kumagai.
Lloyd was close to a hat-trick with a thumping effort but Mana Iwabuchi got clear in the box and Solo saved brilliantly.
Japan: Fukumoto, Kinga, Iwashimizu, Sameshima (Iwabucki, 77), Sakaguchi (Tanaka, 59), Miyama, Kawasumi, Sawa, Ohno (Maruyama, 86), Ogimi.
Unused Subs - Yano, Takase, Kaihori, Ando
USA: Solo, Rampone, O'Hara, LePeilbet, Lloyd, Boxx, Morgan, Wambach, Rapinoe (Cheney, 57), Buehler (Sauerbrunn, 80), Heath
Unused Subs - Mitts, Rodriguez, Barnhart, O'Reilly, Leroux
Pictured - USA celebrate the opening goal. (Gavin Ellis/tgsphoto.co.uk)
She Kicks - the online news service for women's football