As Clark surged to a four-shot halfway lead, no Australians made the cut for the first time since 1959 after Cameron Smith, Min Woo Lee, Lucas Herbert and milestone-man Adam Scott all floundered at beastly Shinnecock Hills.
There were no such troubles for Clark as the 2023 champion apologised for an infamous locker-room meltdown after seizing command on a marathon day for the runaway leader.
Clark initially had a four-shot buffer slashed in half after returning early on Friday morning to conclude his weather-delayed first round, before wrestling back control.
The 2023 winner followed up his opening 64 with a second-round 69 to move to seven under and open his huge advantage over fellow Americans Xander Schauffele (71-66), Sam Stevens (68-69), England's Matt Fitzpatrick (67-70) and South Korean star Tom Kim (70-67).
Clark was embroiled in controversy last year when caught destroying multiple lockers after missing the halfway cut at brutal Oakmont Country Club.
But the 32-year-old has been a picture of calm and control in separating himself from the field so far this week.
"I've gotten a lot of grief since last year - rightfully so," Clark said.
"The thing that's unfortunate is that's not who I am, what happened last year.
"I'm hoping I can win back the fans that I had, or some new fans, because it was a terrible incident.
"I really feel like I can show people that I'm fun and outgoing. I'm fierce, competitive, love the game, respect the game, and I just had a bad moment."
While well in charge, the 32-year-old will need to retain his nerve over what will surely be a testing weekend as he tries to fend off a swathe of serial major winners hunting him down.
As well as two-time major champ Schauffele and in-form 2022 US Open champ Fitzpatrick, Clark has several other heavyweights in pursuit.
Collin Morikawa soared to two under with a sizzling second-round 65 to be solo sixth, five shots back, with fellow dual major winner Justin Thomas (71-68) one stroke further behind.
Bidding to complete golf's career grand slam, world No.1 Scottie Scheffler moved ominously into a share of 11th at even par with a 68 on Friday.
But Clark presumably won't have to worry any longer about Dustin Johnson after the former world No.1 and the leader's closest first-round challenger endured a dramatic day-two collapse.
A winner at Oakmont in 2016, Johnson rolled back the years to post an opening 66 after finishing with two late birdies to briefly cut Clark's lead to two shots.
Johnson remained at four under through 10 holes of round two but the former US Open and Masters champ then dropped eight shots in four holes, including a quadruple-bogey eight on the 15th, to plummet to three over with a horror 77.
Australia will have no one featuring at the weekend for the first time since Bruce Crampton, the country's only representative, missed the cut at Winged Foot 67 years ago.
At six over, Smith (75-71) and his LIV Golf Ripper GC teammate Herbert (74-72) both missed the cut by two shots.
Lee (74-73) was a further shot back, while Scott (73-75) slumped to eight over on his landmark 100th consecutive major appearance.
Two-time champion Bryson DeChambeau and former world No.1 Jon Rahm were among the other big names to bomb out.
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