6-3, 6-4 victory over Querrey to give the Aussies a 3-1 lead.
Sock, who has played 5hr 34min of tennis in two days, is scheduled to play Kyrgios first-up, with John Isner to take on Thompson in the fifth and final match.
Belgium or Italy await Australia in the semi-finals, with the Belgians leading the tie 2-1 going into day three.
The victor of the this quarterfinal will go on to play either Belgium or Italy in the semifinals, to be held in September.
Courier said his team would rally around Sock and noted that his United States team had lost to Croatia previous year from two matches up after the first day.
Nick Kyrgios played a big part in the win as he put Australia in the Davis Cup semi-finals with a 7-6 (7-4), 6-3, 6-4 victory over Sam Querrey, the world No.25, making the score 3-1.
10sBalls Top Stories In Case You Missed It The United States and Australia will be facing each other in the Davis Cup competition for the second time in as many years when they meet again during quarterfinal action this week.
Nick Kyrgios anchored Australia's win with victories in both his singles matches.
The controversial Kyrgios, whose on court behaviour has led to a host of criticism from fellow players, commentators and fans, was the model of decorum and dedication in his two matches.
Taking on the highly-fancied world number 15 and USA number one Jack Sock, the Cherrybrook tennis star in just his second Davis Cup tie won 6-3, 3-6, 7-6 (7-4), 6-4 in just over three hours.
France need to win just one more rubber to eliminate Great Britain, who are severely weakened with the absence of Andy Murray.
The Americans hit back in the doubles yesterday but Kyrgios, who has been in superb form this week, was too good for Querrey and wrapped up the match in two hours, five minutes. I played well on clay a year ago, had a couple of good results.
Australia are seeking a first Davis Cup title since 2003.
US Davis Cup captain Jim Courier added: "I'm super proud of these guys today but it still will take a monstrous effort from us on day three". "Playing for your country, there's no bigger honor in tennis". After Murray served out the second set to pull the Brits even, Murray double-faulted on set point to give France a 2-1 lead after a hard-fought third set.
Pouille, the world number 17 and his team's top singles player in the absence of Jo-Wilfried Tsonga and Gael Monfils, swept the breaker before dominating the decider.