A record home Matildas crowd of 36,109 fans packed Accor Stadium but they were silenced after just 24 seconds when Ashley Hatch pounced on a series of defensive lapses to snatch the lead.
U.S. goalkeeper Casey Murphy, the first of four debutants in a second-string line-up, denied Australia at every turn.
"[She] gave a lot of confidence to the backline, gave a lot of confidence to the coaching staff too," USWNT coach Vlatko Andonovski said after the match.
Tameka Yallop wore Australia's captain's armband, and Gustavsson turned to 17-year-old debutant Jessika Nash and 19-year-old Courtney Nevin, in her sixth cap, in the centre of defence with Alanna Kennedy (quadriceps) and Clare Polkinghorne (rested) unavailable.
The young centre-back pairing received a baptism of fire when Australia turned the ball over shortly after kick-off.
Nash didn't get enough power behind a clearing header, and Lynn Williams nodded the ball on for a surging Hatch, who had escaped Nevin's attention.
Hatch burst past Nash, took a good touch, and finished cleanly past Teagan Micah.
The teams traded chances as the game opened up, and Sam Kerr forced a top-drawer save from Murphy with a brilliant, powerful effort in the 33rd minute.
Then in the 35th minute, U.S. forward Margaret Purce got away on the break but completely mis-hit her shot
Kyah Simon spurned a gilt-edged chance three minutes later, blasting a close-range effort over the bar after a terrific run and cut-back from Caitlin Foord.
"As a striker, you pride yourself on scoring goals and I take full responsibility that I should have finished that," Simon said postmatch. "The game [would have been] 1-1 at that point, so that could definitely change the momentum of the game."
Late in the half, the ever-exciting Mary Fowler forced a big save from Murphy with a fierce shot.
Minutes after the break, Purce cleverly outbodied Nevin then cut the ball back to Lavelle, who finished coolly at the near post.
Kerr started the game despite a limited build-up, while Matildas players also wore black armbands after the striker's uncle passed away during the week.
She was replaced by Kyra Cooney-Cross in the 63rd minute.
Shortly after, Horan went down under contact from Carpenter then buried the penalty.
It was the 35th goal Australia have conceded in 15 games under Gustavsson.
Fowler tried her luck from long-range in the 69th minute but Murphy again stood tall to deny the 18-year-old and seal her clean sheet.