The Wallaroos have suffered a disastrous 32-25 loss to the United States in their Pacific Four clash, which will likely see them miss qualification for the elite WXV 1 rugby competition.
Playing their second Test under new coach Jo Yapp, the Australians looked in control at Melbourne's AAMI Park on Friday night, leading 20-8 at halftime.
But the Americans ran in four second-half tries to secure their first win of the four-team competition.
Layne Morgan was held up over the line in the 76th minute as the Wallaroos desperately hunted a try to level the score.
The Wallaroos now need a win in their final-round match in Auckland over New Zealand, who they have never beaten, and to also collect a bonus point to avoid finishing last in the Pacific Four.
If they don't the Australians will be relegated to the WXV 2 league in South Africa in September-October, while the USA, Canada and New Zealand will join the top three teams from the women's Six Nations in WXV 1 in Ottawa, Canada.
Yapp was delighted with her team's first-half showing, but said the USA were allowed to control the second stanza.
"It was a game of two halves - in the first half we showed a big improvement from last week and we were playing the way we wanted to play," the former England halfback said.
"Second half we just didn't get a good foot-hold early on and we didn't exit cleanly, and unfortunately we ended up chasing the game.
"It was a game we wanted to win, but we now look at WXV 2 and that's a different challenge for us and one we will step up to.
"These are tough lessons to learn."
The Wallaroos fell to Canada in their opening match in Sydney last round, but fancied their chances against the USA, who at world No.10 were ranked five places lower.
They got off to a flying start with winger Desiree Miller crossing in the fourth minute, before flanker Ash Marsters pushed the lead out to 12-3 with a surging run to the line.
After her first try attempt was denied, there was no stopping Maya Stewart a few minutes later for the home side to take a 14-point lead.
The United States, coached by former Wallaroos assistant Sione Fukofuka, scored their first try through hooker Kathryn Treder, but the Wallaroos looked comfortable at the break.
American prop Hope Rogers crashed over for two tries within the opening eight minutes of the second half for her team to level.
The Wallaroos edged ahead with Georgina Friedrichs crossing after a strong carry by Piper Duck, but the visitors kept coming.
A converted try in the 62nd minute by winger Lotte Clapp gave them a 27-25 lead, which they extended seven minutes later through centre Mata Hingano.
Despite plenty of time left on the clock, the Wallaroos weren't able to add to their tally.