Winger Aura Muzzo led the way for the Italians in Whangārei with two tries as they came back from 5-0 down early on to get over the line by 12 points in the end after a cracking encounter.
The match between sides sitting fifth and sixth in the World Rugby Women’s Rankings powered by Capgemini was always going to be a close contest - and so this game proved.
It was the sixth-ranked USA who got off to a brighter start and they were down by the Italian try-line early in the encounter.
During one of the USA's many early phases of attack Italian flanker Ilaria Arrighetti was injured and had to be replaced by Francesca Sgorbini.
That was in the fourth minute and just 60 seconds later the USA were ahead when second-row Hallie Taufoou went over from short range. Fly-half Gabriella Cantorna missed the conversion.
They then continued to have large patches of possession but could not add to their early try as the Italian defence stood firm.
The way they were defending clearly fired up Italy because they started to get a foothold in the game in an attacking sense.
The USA defenders were also doing a good job, but Italy managed to make a breakthrough just before half-time.
They created an overlap by going through the phases and using their big ball carriers and when they put a bit of width to their play full-back Vittoria Ostuni Minuzzi dotted down for a try.
Centre Michela Sillari is known as one of the best kickers in the world and she was on target with the conversion to give Italy a crucial 7-5 lead at the interval.
That late first-half score clearly gave Italy confidence and they started the second period well.
They got more reward in the 50th minute when Muzzo scored their second try. Sillari could not convert and the Italians were 12-5 up.
With 23 minutes to go, Italy were reduced to 14 players when Minuzzi was yellow-carded by referee Hollie Davidson for a deliberate knock on.
The USA took advantage to score their second unconverted try through second-row Jenny Kronish.
Italy reorganised, though, and managed to score their third try while they were a player down. Muzzo got her second after a great run and they were 17-10 up by the time Minuzzi returned to the fray.
And with 10 minutes to go another excellent run – this time by Muzzo’s fellow winger Maria Magatti – saw Italy score their bonus-point securing fourth try.
After the game Italy captain Elisa Giordano said: “I would just like to thank my team for this performance and their hard work and we will build from here now.”