One, clapping all six American goals, was First Lady Jill Biden.
Another quiet observer was Matildas coach Tony Gustavsson -- a man arguably more accustomed to watching the world champions from the sideline than the stands -- ahead of Tuesday's crunch match against the world No. 1 ranked team.
Before he was named Australia coach in September 2020, Gustavsson was USWNT assistant coach in 2012, then again between 2014 and 2019, with two Women's World Cup triumphs and an Olympic gold medal to show for it.
There's little change in U.S. personnel since Gustavsson's departure -- only five of their 22-player Olympics squad weren't 2019 World Cup champions -- and he'll have to lean on every bit of inside knowledge for the reunion with his former team.
"In this business you have a lot of former colleagues and friends that you meet," Gustavsson told AAP.
"It's one of those where before the game and after the game it's going to be nice to see some friends and former colleagues, but then when it's game time, it's go time.
"We want to test ourselves against the best, and we have an opportunity here as the Matildas to test ourselves against the best."
A draw should see the Matildas progress as one of two best third-placed teams to play the Group E winner -- either Great Britain or Canada -- as should a loss, but the latter would see them face a nervous wait on results in other groups.
But for now their fate will be in their own hands from at Kashima Stadium on Tuesday.
"We showed in both these opening games now that we are very true to who we are as a team -- we're ready to play our best with the crest on the chest and leave it all out there," Gustavsson said after losing to Sweden.
"We're a pressing and aggressive team, we're an attacking-minded team.
"We'll go about [the U.S.] game as being ourselves and hope that we're good enough to beat them -- we know we can if we play our A game."