A brace from Sophia Smith and one goal from captain Lindsey Horan sealed The Stars and Stripes' victory.
However, as coach Mai Đức Chung said before the match, "It's not about the result, but the way we play, the mentality against an opponent at this magnitude," and the Golden Star Women Warriors' brave performance won the hearts of Vietnamese fans everywhere.
Trần Thị Kim Thanh, Việt Nam's goalkeeper, was perhaps the embodiment of that spirit. The 1.65m keeper saved a penalty from Alex Morgan, one of the greats of the women's game.
Many changes were made to the starting line-up by Chung after Việt Nam's 0-9 loss to Spain on July 14. Dương Thị Vân, nicknamed "Vân Kanté" for her immense coverage and control of midfield, was benched after a head collision with teammate Phạm Hải Yến in training.
Fans even came all the way from Hải Phòng to Auckland to support the women in red. At home, the New Zealand and Australian embassies hosted a "Breakfast Watch Party" for fans to watch the game in Hà Nội.
With all of that support, Việt Nam started strong in the first 10 minutes, denying chances by Lindsey Horan and her teammates.
But at the 14th minute, USA found their breakthrough when Alex Morgan's through ball found 22-year-old Sophia Smith free, and she scored with a low driven shot that went through Kim Thanh's legs.
After the goal, Vlatko Andonovski's girls turned on the pressure with shot after shot, but Kim Thanh's heroics spared Việt Nam.
Thanh was tremendously good in this game, but when the keeper is the best player on the field, it's never a good indicator.
In the 39th minute, Hoàng Thị Loan made a challenge and Trinity Rodman went down inside the box.
Moroccan referee Bouchra Karboubi had to check VAR, and after she saw that Loan's foot touched the legs of Dennis Rodman's daughter before the ball, Karboubi pointed at the spot.
Alex Morgan, a two-time World Cup Winner, took the responsibility, but her shot was low and saved by Kim Thanh. The Vietnamese players rushed to Thanh later to celebrate, as if they had scored a goal against the World No.1.
The joy was short-lived, however, as in the sixth minute of added time, the USA got their second goal courtesy of Smith. The goal was deemed offside at first, but VAR led Karboubi to reverse the decision. The United States led 2-0 before the break.
The second half started with the USA continuing their domination. Numerous chances came for Andonovski's team, and one even forced Kim Thanh to make a stunning triple save.
Việt Nam's defence was perhaps stronger in the second half, and even got chances to counter, but the difference in skills and strength denied Huỳnh Như and her teammates even a clear cut chance at Alyssa Naeher's goal.
In the 77th minute, a rare mistake from Chương Thị Kiều was capitalised by Smith, who passed to Horan for a tap into the empty net which made it 3-0 for the USA.
Andonovski brought on Rose Lavelle and Megan Rapinoe in the final minutes, hoping to score more goals to take advantage before meeting Holland in their next match in this "Group of Death", but both Rapinoe and Lavelle squandered their chances.
Even with nine minutes added on, no further goals were scored and the match ended 3-0 to the United States.
"We kept our promises to the fans," said coach Chung after the match. "I am happy because of the team's mentality and how we stuck to our game plan today."
"Every minute of that game was fun and the crowd was amazing," said Player of the Game Sophia Smith, who scored a brace on her debut.
"We could have scored more goals, but it's the World Cup and not everything is perfect," Smith added.
Việt Nam will have five days to recover before facing Portugal on July 27. The USA, on the other hand, faces Holland next in a rematch of the 2019 Women's World Cup Final. /.