The US have the strongest overall team in the mixed international competition and emphasised their status as favourites with a 5-0 thumping of Poland.
After victories for Frances Tiafoe and Jessica Pegula, who stunned world number one Iga Swiatek, on Friday, Taylor Fritz booked their passage through to the final in Sydney with a 7-6 (5) 7-6 (5) victory over Hubert Hurkacz.
They did not allow their opponents any consolation, with Madison Keys defeating Magda Linette and Pegula and Fritz teaming up for a final doubles victory over Lukasz Kubot and Alicja Rosolska to complete the rout.
Italy earned their place in the last four as the best losing team from the city finals and have made the most of their second opportunity, seeing off Greece 4-1.
Martina Trevisan's epic victory over Maria Sakkari on Friday set the tone and, although Stefanos Tsitsipas battled to a 4-6 7-6 (2) 6-4 victory over Matteo Berrettini, Lucia Bronzetti sealed their final spot by beating Valentini Grammatikopoulou 6-2 6-3.
"It was not easy, because it was the most important point," Bronzetti said. "I felt pressure because I had to win.
"I knew that it would have been a tough match. I'm proud of myself, because I think that I had a good attitude in the court, and I also played good."