Australia's hopes were dented when Cameron Burgess turned the ball into his own net in the 11th minute, before Alex Freeman's 43rd-minute goal delivered the hammer blow at Seattle Stadium.
At halftime, it earned a lashing from Socceroos great Harry Kewell.
"It's not good enough," Kewell told SBS.
"It feels like we've frozen on the big stage."
Australia were vastly improved after the break, buoyed by the introduction of substitutes Nestory Irankunda, Connor Metcalfe and Jason Geria.
But the damage was done, leaving the Socceroos likely needing a result against Paraguay on Friday (AEST) to progress to the knockouts.
US pundit Mike Grella, who famously dismissed this game as a "layup" for the US after December's draw then seemingly revelled in his role as chief agitator, took a victory lap.
"This is the United States of America over here," Grella told CBS.
"Everybody wants to compete, everybody wants to believe… at the end, the football spoke, 2-0, thank you very much."
Socceroos coach Tony Popovic conceded the Americans were "quicker", "more powerful" and "won every duel".
"I don't know if it was the occasion, but we looked sluggish, heavy legged," Popovic said.
Defender Geria lamented how his side failed to get a foothold in the game.
"I don't know about 'struggled with the occasion' - but I definitely think the US were up for it," Geria said.
"They were backed by a huge home crowd and I think we just came out a bit flat."
Skipper Harry Souttar was frustrated the Socceroos couldn't find a way to deal with the "aggressive" and "sharp" US press.
Popovic's decision to bench Irankunda and Metcalfe in favour of Nishan Velupillay and Mathew Leckie didn't pay off, with Mohamed Toure isolated in attack and Australia lacking drive.
Former England star Wayne Rooney didn't mince his words while analysing the lopsided contest at halftime.
"USA have been excellent, but Australia have been awful," Rooney said on the BBC.
"They can't cope with the high press, and leaving the two wide men out means they've got no outlet, they've got nowhere to go."
Rooney later added: "When you're not one of the big nations, you have to play your best team in all the group games to try and get out of the group.
"... I think he's messed up tonight."
Toure, hooked at halftime, said he'd struggled.
"I felt a bit alone. It was just tough. They're (the US defenders) big boys, they're strong and physical," Toure said.
"And having to battle them alone … I struggled a bit with that and it was a bit frustrating."
11°C