World number nine Taylor Fritz battled past Italian Matteo Berrettini with a powerhouse performance to steer the United States to the inaugural mixed teams United Cup title in Sydney on Sunday.
Frances Tiafoe and Jessica Pegula both won their singles rubbers to give their country a 2-0 lead with Fritz delivering victory by winning 7-6 (7/4), 7-6 (8/6).
Madison Keys made it a clean-sweep 4-0 with a 6-3, 6-2 win over Lucia Bronzetti.
"It's amazing for the team to win this event, we came in with really high hopes," said Fritz.
"Really happy to be in the position to clinch the match. The emotions when you win are amazing.
"We had a lot of team bonding this week," he added. "When we combine the guys and girls from the US we are so deep through the rankings it just makes team so much stronger."
The dominant United States crushed the Iga Swiatek-led Poland 5-0 to make the decider of the new tournament -- which began with 18 nations playing round robin matches in Perth, Brisbane and Sydney -- while Italy outgunned Stefanos Tsitsipas's Greece 4-1.
Fritz constantly put pressure on the Berrettini serve, earning four break points on his first two service games, but all were saved.
Despite the American being in charge from the baseline, it went to a first set tiebreak where he got two decisive early breaks to move 3-0 ahead before closing out the set.
Fritz again created a series of break points in the second set, but Berrettini hung on and it again went to a tiebreak where he once more prevailed.
Women's world number three Pegula, who burst into the top 10 in 2022 by winning the WTA 1000 Guadalajara tournament, stormed home 6-4, 6-2 against Martina Trevisan.
"Definitely very relieved, first match of the day, first match of the final," said Pegula.
"Martina is playing great, she's a fighter, I feel like she's thriving on the atmosphere with the fans and her team and really hard to beat someone like that.
"Glad I was able to play well enough to get the win."
- High level -
Trevisan stunned world number six Maria Sakkari in a gripping three-hour encounter on Friday, and her confidence was high.
But Pegula was also in red-hot form, toppling world number one Swiatek for the first time in the semi-finals.
She came out firing against Trevisan, racing to a 3-0 lead after breaking the Italian's opening serve.
Trevisan showed the fighting qualities that helped her beat Sakkari to claw back, converting a break point in the fifth game and holding serve to get it back on level terms.
They exchanged breaks again on the fast hard courts before Pegula pounced once more to clinch the set on the Trevisan serve with a backhand winner.
It was all Pegula in the second as she put her foot to the floor, racing 5-0 clear.
But the Italian refused to give up and broke back as the American served for the match before her comeback faltered.
Tiafoe picked up where Pegula left off, surged through the first set 6-2 against Lorenzo Musetti before the Italian retired due to a right shoulder injury.
He broke Musetti's serve early, with the Italian increasingly touching his right shoulder as the set wore on before receiving treatment and calling it a day.
"I thought it was a really high level ... obviously at the end there I could see he was touching his shoulder a lot," said Tiafoe. "I didn't want to win this way. I hope Lorenzo feels better."