The Australian Boomers have overcome the early loss of Aron Baynes to post a famous 91-83 win over the United States in an Olympic warm-up match in Las Vegas.
Baynes went down clutching his right knee in the opening minutes of Tuesday's match and the Toronto Raptors centre played no further part.
It leaves the Boomers sweating on his fitness ahead of the Tokyo Olympics.
The Boomers trailed by 11 points late in the second quarter, but produced a mesmerising second half to snatch victory.
Philadelphia 76ers guard Matisse Thybulle was impressive at both ends of the court with 12 points, three assists, three steals, and two blocks for Australia while Melbourne United sharpshooter Chris Goulding (11 points) lifted when the Boomers needed him in the third quarter.
Nick Kay played a key role with eight points and nine rebounds, and Duop Reach (nine points) helped fill the void left by Baynes.
The USA lost to Nigeria 90-87 in their first warm-up game, and the defeat to the Boomers means they have now slumped to back-to-back losses in a worrying sign as they bid to snare a fourth straight Olympic gold medal.
Portland star Damian Lillard scored 22 points on 6-of-11 shooting from long range and Kevin Durant nailed four long bombs on the way to 17 points, but the USA struggled for fluency against a dogged Boomers defence.
"We're not satisfied. we've got a long way to go," Mills told ESPN after the match.
"We can still get a lot better. But defence is where we're going to hang our hat this whole campaign.
"We believe in our entire team, and everyone being able to step on the floor and make an impact.
"We're deep. And yes, not a lot of people might know people on our team. But for them to come in and make big plays is a credit to how much work we're putting in together, and trusting and believing in each other."
Ingles started the match in hot form, nailing three long bombs to help give the Boomers a surprise 13-7 lead.
But Lillard replied in kind, helping edge the USA ahead 27-24 by quarter time.
The second quarter was a defensive struggle until the USA pulled away late for a 46-37 lead at half-time.
Durant and Lillard nailed two three-pointers each early in the third quarter to keep the Boomers at bay, but the Australians went on a 19-6 run to finish the quarter to take a shock 69-64 lead into the last.
Sharpshooter Chris Goulding was crucial in the run with two three-pointers, including a mesmerising buzzer-beater that lifted the Boomers' bench to its feet.
Durant stayed hot from long range to help the USA retake the lead with less than five minutes remaining in the match.
But Mills stepped up to the plate when it mattered most, scoring a series of clutch baskets to help guide the Boomers to victory.