Mounted police were forced to intervene after fans attempted to breach barriers at Melbourne's Federation Square when the popular site reached capacity just after 4am on Saturday.
About 7500 punters packed the site in cold and rainy conditions, with 14 flares and one firework set off before the match, leading to two arrests.
The pair will be charged on summons, with police reviewing CCTV to identify those responsible for setting off the remaining flares.
"Enforcing prohibited items such as flares from entering the live site remains the responsibility of the venue," a Victoria Police spokeswoman said.
While fans celebrated the atmosphere, there was disappointment as the Socceroos' campaign suffered a setback with a 2-0 loss to the American team.
Former Socceroo Craig Foster, who was the MC at the live site, urged fans to stop letting off flares.
There were no reported injuries, however a police officer sustained a foot injury after being crushed against a barrier.
A 16-year-old boy was also arrested in relation to an alleged sexual assault of a woman about 4.55am.
One shirtless man was seen being escorted away following a confrontation.
Many of those in the large crowd donned ponchos and green and gold scarves, with one fan in a costume that made it look as though he was sitting on Donald Trump's shoulders.
Almost 9000 eager fans were redirected to AAMI Park, where the match was also livestreamed.
World Cup fever also spread across several live sites in Sydney, with multiple flares set off at Tumbalong Park in the CBD.
A 20-year-old man needed urgent medical attention and was taken to hospital for further treatment after being hit in the face with a flare.
Two men, aged 20, were arrested at the scene and later charged with possessing a bright light distress signal in a public place.
They were granted bail and are due to appear in court on Wednesday.
Conditions were more relaxed at Brisbane's South Bank, where thousands of fans watched the blockbuster clash, while excited crowds also gathered in Hobart and Canberra.
Australians abroad also flocked to Socceroos watch parties around the world.
Socceroos fans Jack Murata, Alex Golfman, and Nicholas Konarski, all from Sydney, joined hundreds of others at a pub in San Francisco to cheer on the national team.
Beers in hand and wearing the green and gold, punters were still smiling despite the loss, with sights firmly set on the Socceroos' next match against Paraguay on Friday Australian time.
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