Former City star Carli Lloyd bagged a brace in Kashima with Megan Rapinoe also netting twice, while Sam Kerr, Caitlin Foord and Emily Gielnik were on target for the Matildas in a seven-goal thriller.
Dahlkemper was an unused substitute, while former Blues Lloyd, Sam Mewis and Rose Lavelle all featured to help the Stars and Stripes to clinch their sixth medal of seven at the Olympic Games.
The clash bore a stark contrast the the goalless draw the two sides had played out in the group stage.
Rapinoe opened the scoring on eight minutes, finding the net straight from a corner, after Teagan Micah had tipped a Christen Press effort over the bar.
Press almost made it two but was thwarted by Micah once more, before Australia equalised through Kerr.
The forward latched onto Foord’s pass before firing past Adrianna Nichole Franch to become the Matildas’ all-time top goalscorer with 48.
She almost turned the game on its head with a header – only to be denied by Franch – but Australia’s respite was short-lived as the USA regained the lead with Rapinoe's second of the game: a sweetly-struck volley from Alanna Kennedy failed clearance.
Lloyd – aged 39 – made it three before half-time with a superb finish, collecting Lindsey Horan’s through-ball and drilling into the far corner.
The USA continued where they left off after the break when the two-time FIFA World Player of the Year then doubled her personal tally, capitalising on another Kennedy error and poking through the legs of Micah, to write her name in the history books once more as her country’s all-time top Olympic goalscorer.
Australia fought back with a Foord header three minutes later and were unfortunate not to make it 4-3 when a Kerr header bounced back off the post.
Lloyd thought she had completed her hat-trick – only to see her low drive disallowed for offside – and Gielnik made for a nervy finish with the goal of the game on 90 minutes, cutting inside and rocketing an effort into the back of the net.
Despite a late flurry of Australian pressure, the USA hung on to clinch bronze.