Ryder Cup teammates Patrick Reed and Jordan Spieth charged up the leaderboard, but the American assault on Friday didn't include Tiger Woods who crashed out of the U.S. Open.
The two Texas natives were co-leaders after 36 holes at the $10 million tournament at the 7,695 foot Chambers Bay golf course, the longest in major championship history.
The 24-year-old Reed had a 69 for a five-under total of 135, joining reigning Masters champion Spieth, 21, who had a fine 67.
“Anytime I play with Jordan I enjoy it,” said Reed. “The main thing for me is to stay focussed
“I am in a good position and I hopefully can have a good week-end and a chance to win.”
Overnight co-leader Dustin Johnson was one stroke adrift with a 71 as he was tied with South Africa's Branden Grace (67) who was the only non-American in the top four. U.S. golfers held eight of the top 11 positions on Friday.
Grouped on 137 were U.S. trio Tony Finau (68), Daniel Summerhays (67) and Ben Martin (70) and Joost Luiten of the Netherlands (69).
The two young Americans Spieth and Reed formed a successful Ryder Cup pairing against the Europeans at Gleneagles, Scotland in late September.
World No. 2 Spieth is once again proving he can shine on the biggest stage as he surged up the leaderboard by making birdies on three of four holes beginning at No. 14.
Spieth, who posted a wire-to-wire victory at Augusta in April, is seeking to become the first man to win the Masters and U.S. Open in the same year since Woods in 2002.
“If you shoot in the 60s at a U.S. Open you are going to be pleased,” Spieth said. “I will draw on my experience at Augusta, but my patience here has to be that much higher.
“At Augusta I was making everything. It would be nice if I could do that here. This course is going to get tougher and tougher.”
There was some drama on the final hole of the day for Spieth's threesome when playing partner Jason Day, of Australia, collapsed on the side of the fairway after suffering a bout of vertigo.
The Queensland native was treated by several medical staff on the course for about 10 minutes before mustering enough courage to finish out his round despite being in obvious discomfort as he made those final shots.
His manager Bud Martin said Day, who shot a 70, expects to be well enough to resume his tournament the next day.
Reed also climbed up the leaderboard on Friday as he briefly held the tournament lead, but a bogey at the last dropped him into a tie with Spieth.
Reed, who proclaimed himself as one of the “top five players in the world” after winning the WGC-Cadillac Championship in March of last year, would like to validate that boast with his first major title at Chambers Bay.
Reed had a chance to hold onto the 36-hole lead but his 18-foot putt for par on 18 stopped on the edge of the cup for a tap in bogey.
Johnson had three birdies on the front nine and appeared to be headed into the week-end with at least a share of the lead.
But the long-hitting American had a frustrating finish with back-to-back bogeys on 17 and 18 to drop to a tie for third.
“When I got into trouble I felt I hit good shots and got myself out and made some good up-and-downs,” said Johnson, who is considered one of the best players who hasn't won a major.
“But I just didn't hole the putts like I did yesterday.
The Indian duo of Anirban Lahiri and Shiv Kapur made an early exit after missing the halfway cut.
The Indians played well in patches but were hit on putting surfaces, which in general was very demanding for everyone in the field.
Lahiri scored 75-72 while Kapur shot 72-77. The cut came at five-over and Lahiri missed it by two and Kapur missed it by four.
Lahiri looked set to make his second cut in a Major this year till the 12th hole of the second round before running into a rough patch on the second nine, when he bogeyed three times in six holes to miss the cut by two.
Lahiri shot 75 and 72 and at 147, he fell short by two, as 75 players made the cut.
The top 60 and ties made the cut.
Shiv Kapur, who came through a qualifier, had another disastrous start, this time from the tenth. He dropped shots on three of his first four holes — the 10th, 11th and 12th.
A birdie on 15th was his lone consoling moment of the day, as he added bogeys on 18th, first and then three in a row from fifth to seventh for a 77 after his first round 72 that saw him finish at nine-over 149 and way off the cut mark.
“I had my chances, but it just did not happen. I was placed alright after the second birdie on second, but the last six holes had three bogeys and I missed some smallish putts for birdies and pars,” Lahiri said.
Kapur said: “Nothing worked for me and I was disappointed.
Longest major in history The USGA wanted a more difficult second round after 25 players broke par on Thursday. So they extended Chambers Bay to 7,695 feet, making it not only the longest ever U.S. Open but also the longest in major championship history.
The front nine alone was 4,020 feet. They also made the first hole a par-five instead of a par-four and altered 18 so that it became a tricky par four.
World No. 1 Rory McIlroy and six-time U.S. Open runner-up Phil Mickelson both punched their tickets into the week-end.
McIlroy was making no progress from the two over mark he started the day on until he eagled the par-four 12th.
But he took a double-bogey at the par-three 17th and settled for a second straight 72 and a four-over total which got him into the week-end.
Woods wasn't so lucky as he had the door slammed shut behind him.
Woods added a 76 to his opening 80 and, at 16 over par, he was on his way home after another disastrous tournament, tied for 150th place.
Mickelson fired a four-over 74 to keep his bid for a career Grand Slam alive.
Other notables missing the cut were Rickie Fowler, defending champ Martin Kaymer, Bubba Watson and 15-year-old amateur Cole Hammer.
Top second round scores: 135: Patrick Reed (66-69), Jordan Spieth (68-67); 136: Dustin Johnson (65-71), Branden Grace (69-67); 137: Joost Luiten (68-69), Daniel Summerhays (70-67), Tony Finau (69-68), Ben Martin (67-70).
138: J.B. Holmes (72-66), Jamie Lovemark (70-68), Jason Day (68-70); 139: Alexander Levy (70-69), Henrik Stenson (65-74), Kevin Kisner (71-68), Brian Campbell (67-72), Shane Lowry (69-70); 140: Andres Romero (71-69), Matt Kuchar (67-73), Jason Dufner (68-72), Cameron Smith (70-70).
