Serena Williams and John Isner sent the United States into the Hopman Cup final after completing a 3-0 win over the Czech Republic in Perth.
The USA needed a clean sweep to secure top spot in Group A following Tuesday's defeat by Canada and in securing it ended the Czechs' participation in the tournament.
Williams had been swept aside by Eugenie Bouchard against Canada but the world No 1 showed her battling qualities in a 6-3 6-7 7-6 win over Lucie Safarova.
Isner extended the advantage with a 7-6 6-4 victory against Adam Pavlasek before the US pair combined in a convincing 6-3 6-3 win over the Safarova-Pavlasek partnership.
Bouchard followed up her impressive win over Williams by beating Flavia Pennetta as Canada ended their campaign with a 2-1 win over Italy.
The 20-year-old, who won 6-3 6-4 without losing her serve, said: "Each game was kind of like a battle and I'm happy I was able to keep my serve in the second set. She was really putting pressure on me.”
Vasek Pospisil made it 2-0 with a 6-0 6-3 victory over Fabio Fognini, before Italy won the concluding mixed doubles in three sets (3-6 6-3 10-7).
Group B, which includes Great Britain, will be decided on Friday when Poland can guarantee their place in the final with victory over France.