Butt scored the only goal of the game in the 67th minute.
Emily Van Egmond flicked a ball over the American defence to the waiting Butt, who steadied and lashed the ball past Alyssa Naeher from short-range.
The landmark result ends the USA’s long domination over Australia in women’s soccer.
Not in 27 previous meetings had the Matildas beaten the US, and not in 12 years had Australia even drawn.
But the effervescent display will have Alen Stajcic’s side dreaming of bigger things at next year’s Asian Cup and the 2019 World Cup.
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Katrina Gorry was bright in midfield, Sam Kerr took it up to the American defence and Caitlin Foord was busy.
Alanna Kennedy’s strong defensive marshalling ensured the Matildas could field a back three with confidence against the world No.1 side.
Lydia Williams was immense in the Australian goal.
On 11 minutes, she denied in-form veteran Megan Rapinoe with a one-handed stop at the near post, following that effort up with two strong saves to deny substitute Carli Lloyd.
But her finest moment came with five minutes remaining when she produced a one-on-one save to stop Crystal Dunn with a trailing leg.
The hosts finished the stronger as they desperately sought an equaliser.
It never came, putting Australia on top of the standings after the opening day of the US-based friendly tournament.
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The earlier match between Japan and Brazil — the Matildas’ next opponents — finished 1-1.