The USA, which had already lost Hawaiian striker Tani Costa on the eve of the tournament with an ankle injury, had midfielder Erika Tymrak go off with a hip injury 30 minutes into the game.
As substitute Elizabeth Eddy waited at midfield to come on, Japan equalized when Chiaki Shimada's brilliant strike from 35 yards out slammed off the crossbar and rebounded into the middle of the U.S. penalty area, where Mana Iwabuchi scored on the rebound.
Star Kristie Mewis put the United States ahead in the 51st minute with a shot from 22 yards that wrong-footed Japanese goalkeeper Saki Nakamura, but Japan equalized in the 68th minute on a spectacular strike by Natsumi Kameoka from 36 yards.
Six minutes later, Japan went ahead for the first time on another brilliant strike. Akane Saito flicked the ball with her head to substitute Kei Yoshioka, who settled with her chest at the top of the penalty area and hit a sizzling volley into the upper left corner.
Next up for the USA: Paraguay Sunday back at Hamilton's Waikato Stadium.
In the second Group C game, France scored three goals in the first 17 minutes and went on to beat Paraguay, 6-2, in a game highlighted by Pauline Crammer's hat trick.
In Group D, England upset Brazil, 3-0, with three goals in the last 20 minutes, and Nigeria edged South Korea, 2-1.
Oct. 30 in Hamilton
Japan 3 USA 2. Goals: Iwabuchi 31, Kameoka 68, Yoshioka 74; DiMartino 3, K.Mewis 51.
USA -- Vancil, Brooks, Colohan, Quon, Tymrak (Eddy, 32), Roberts, S.Mewis (Johnson, 86), Laddish (Klei, 52), K.Mewis, DiMartino, Verloo.
Japan -- Nakamura, K.Chiba, M.Chiba, Kishikawa, Kameoka, Shimada (Tanaka, 59), Takeyama, Inoue (Yoshioka, 69), Kira (Hamada, 91+), Iwabuchi, Saito.
Yellow cards: Japan -- Iwabuchi 93+; USA -- 70.
Referee: Thalia Mitsi (Greece).
DAY 1 RESULTS:
Oct. 28 in Auckland
New Zealand 0 Canada 1 (Lamarre 27).
Oct. 29 in Auckland
Denmark 1 (Boye 51) Colombia 1 (Ariza 20).
Oct. 29 in Christchurch
Germany 5 (Mester 17, Marozsan 34, 43, Knaak 51, Kemme 66) Costa Rica 0.
North Korea 1 (Byol 69) Ghana 1 (Dadson 73).
Oct. 30 in Hamilton
Japan 3 (Iwabuchi 31, Kameoka 68, Yoshioka 74) USA 2 (DiMartino 3, K.Mewis 51).
France 6 (Crammer 5, 12, pen. 61, Poulain 17, Augis 58, Catala 86) Paraguay 3 (Gonzalez 45, Genes 90).
Oct. 30 in Wellington
England 3 (Carter 71, 89, Bruton 75) Brazil 0.
Nigeria 2 (Adekwagh 1, Aighewi 60) South Korea 1 (Ji So Yun 85).