Every member of the team had at least three points as USA co-captain Crystal Langhorne's 18 points in 14 minutes led the offensive attack for the second time in five games, while her Maryland teammate Laura Harper had 13 and Jolene Anderson and Marscilla Packer contributed 10 apiece.
"Everybody knows we're big and we're very aggressive," said Langhorne. "Our post play is strong, we rebound the ball so well, not just posts but guards also. I think we have so many weapons – shooters, post players – that it's very difficult to defend us."
Following a day off, the red, white and blue will go up against Belgium (2-3), the fourth placed finisher from Group A on July 6. The semifinals will be held on July 7 and the finals are scheduled for July 8.
"We need to work on our consistency and playing our game," said USA U21 National Team and Duke University (N.C.) head coach Joanne P. McCallie.
"We dominated early and then went on vacation. I felt the second half was incredibly dominant and that's what I'm going to remember about this game, the way our team responded to be so dominant in the second half of the game. We did dominate all facets and we should have dominated all facets. It helped us get better and for the next opponent and that's really what it's all about."
The USA jumped out of the gates strong and opened up a 21-7 lead by the 2:28 mark in the first quarter.
However, the Americans' shooting went cold and after Japan tipped the ball back in – its only put back of the contest – at the buzzer, the USA's lead was 24-15.
The U.S. defense frustrated their undersized opponents for most of the second quarter, enabling its offense to build up another significant lead. After an Abby Waner tip-in at 3:35 the lead was 40-21.
However, a defensive lapse over the final three minutes of the half allowed Japan's Naomi Hayashi to swish in three consecutive long-range threes in an 11-2 run and at the midway break the USA's gap had diminished to 42-32.
"We knew we were bigger, better and faster and we knew we needed to show what we can do," said DeWanna Bonner, who had six points and six rebounds.
"Basically we were focusing so much on their penetration and how quick they were, we forgot all about their threes. It was kind of a shock when she came out and hit the first three and made three in a row, so we had to turn it around at halftime."
The Americans returned to the court determined to make a statement before the medal rounds. With the score still a 10-point difference, 46-36 after two minutes of play, Anderson kicked-off a 10-0 spurt that saw Langhorne get a pair of buckets off of offensive boards, while Packer fed Harper for an easy layup.
Japan immediately called a time out after Harper's bucket in order to regroup. However, McCallie told her troops in the huddle that they need to make a statement now, they can't let Japan back in the game the way they did at the end of the first half.
Japan managed to get off a 3-pointer at 4:38, but the red, white and blue closed out the period on a 14-4 run that saw some great plays.
Not only did Waner connect on her second three of the game and tournament, a few of the other highlights included Essence Carson hitting a jumper, followed by a steal and assist to Anderson, while Lindsay Wisdom-Hylton had a steal that led to a Carson bucket.
By the third quarter buzzer, the U.S. was well in control, 70-43, and outscored Japan 28-14 to seal the win.
"Coach P said everybody brought their ‘A' game and I think she's right," said Wiggins. "Everyone did what they were good at doing. It helped and it gave us some good momentum going into the next round."
Hayashi was held to just one long ball in the second half and finished the game as Japan's leading scorer with 12 points.