Another barrage of huge serves saw Kyrgios steal a march in the second set tiebreak and after running the big American all over the court, he grabbed the set with a cheeky drop-shot.
Sock said he could see more positive signs from his good friend Kyrgios in his stunning straight-sets defeat of John Isner.
Past year was hard for me so I am enjoying tonight.
"I'm only human. I'm not going to change in that department", Kyrgios said.
"I felt like I played well enough to beat anyone out there, but not Nick", Isner said. "I've been playing great tennis and wanted to carry it into today and that's what happened".
The hosts got the crowd back into the game when a rasping Groth forehand return down the line gave Australia a decisive break for 4-2 in the fourth but the Americans would not be denied and muscled up to claim the decider. I've never been able to be consistent.
"People tend to forget that I am only 21".
Thompson won both his two singles matches on debut against the Czech Republic in Australia's February tie, but with a No.79 ranking sits 64 places beneath Sock on the ATP standings.
Australia is now one win away from advancing to the semifinals.
Late substitute Jack Sock and partner Steve Johnson kept the United States alive in its Davis Cup quarterfinal with Australia, beating Sam Groth and John Peers 3-6, 6-3, 6-2, 2-6, 6-3 in Saturday's doubles. Was fatigue an issue?
The American No.2, who owns a Davis Cup win over Roger Federer, clouted the most aces on the ATP Tour previous year, 1159, at an average of 23 per match, the majority of which were best-of-three-set encounters. What did he do well?
"Thommo in only his second live Davis Cup match, that was pretty impressive", he said.
"Just playing within myself, not trying to go too big". It was unbelievable how it happened.
Thompson carried all the momentum with him into the fourth set against an increasingly exhausted looking Sock and closed out the match in three hours. He's an incredible player but I'm a little bit used to the match-up.
"I try and defend him and stick up for him a lot as well, but I love having him in my team."
There's a chance that Courier will choose to scratch one or both players and use a different team, an option every captain has for up to an hour before the tie.
And the American duo made sure the U.S. would live to fight another day when they outlasted the Australian pair 3-6, 6-3, 6-2, 2-6, 6-3.
Sweden: Truck crash into Stockholm store is terror attack
Swedish radio says Friday that three people have been killed in the crash and Swedish broadcaster SVT says shots have been fired. Local health authorities said that one person died in hospital and 15 others, including children, are injured.