Australia's hopes of progression and sealing a top-two berth will come down to their final group match against Paraguay on June 25 (June 26 AEST) after a nightmare afternoon at Seattle Stadium on Friday.
Coach Tony Popovic's call to bench Nestory Irankunda and Connor Metcalfe, who scored in Australia's opening 2-0 win over Turkey, for Nishan Velupillay and Mathew Leckie backfired as the US dominated.
The US, without injured star Christian Pulisic, battered Australia all day and took the lead in the 11th minute through a Cameron Burgess own goal.
Alex Freeman dealt the Socceroos a hammer blow by bundling home a header - that was initially ruled offside but cleared by VAR - to double the co-hosts' lead in the 43rd.
"I don't know if it was the occasion, but we looked sluggish, heavy legged," Popovic lamented.
"They were quicker, they were more powerful. They won every duel, they won every second ball and when you do that, it makes it very difficult.
"Then we conceded two soft goals."
Popovic turned to Irankunda and Metcalfe at halftime but Australia could not claw their way back, while Leckie came off injured on the hour mark to add to the horror show.
The US (six points) lead Australia (three) in Group D, with Turkey and Paraguay facing off on Friday night.
Even without superstar Pulisic (calf), the US were on top in every element, bullying the Australians physically, dominating possession and explosive in attack.
The healthy Australian contingent in the crowd of 66,925 fans were well and truly outnumbered by their deafening US counterparts, and the Socceroos looked intimidated and nervous.
Australia couldn't string passes together and were constantly under the pump.
Seattle Stadium erupted when Folarin Balogun went on a blistering run down the left, cut into the box then squared a brilliant ball that Burgess turned into his own net.
It was a nightmare game for the centre-back, who was uncharacteristically shaky on the ball and hooked at halftime.
The US doubled their lead after a free kick was worked to Sergino Dest at the top of the box.
Dest's shot took a deflection and Freeman rose highest to head home.
It was initially called offside but after a VAR review, it was ruled Freeman was onside when Dest shot, while Balogun was not considered to have interfered with Patrick Beach.
Popovic took off Mohamed Toure, Velupillay and Burgess for Irankunda, Metcalfe and Jason Geria at halftime and saw some improvements.
"The reaction in the second half was outstanding," the Socceroos boss said.
"We had a lot of fatigued bodies in the first. Physically and mentally it was tough, but we did very well in the second half. We created opportunities.
"We were very aggressive, we won all the duels in the second half. So when you do that, you have a chance.
"So that's something to build on for the next match."
Alessandro Circati brilliantly stopped Balogun making it 3-0 in the 51st minute.
Cristian Volpato made his World Cup debut when he replaced Leckie.
Volpato, Irankunda and Metcalfe had some moments, while Geria had a shot blocked, but it proved too little, too late.
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