Webb Simpson and Bubba Watson (U.S.) d. Ernie Els and Ryo Ishikawa (International), 4 and 2
The Americans struck first, with Simpson and Watson closing out Els and Ishikawa on the 16th hole.
The Internationals got out to an early 2-up advantage, taking two of the first four holes. But they would not win another hole for the remainder of the match.
Simpson and Watson reeled off three consecutive hole wins to take control of the match, with all of the putts made by Simpson, the PGA Tour's money-list runner-up.
Admitting nerves on the first tee, Simpson said Watson was able to put him at ease.
The American duo played a bogey-free round of 7 under for their 16 holes together, making them a team likely to be seen again this week.
Adam Scott and K.J. Choi (International) d. Tiger Woods and Steve Stricker (U.S.), 7 and 6
'Unfortunately they got off to a quick start, and this course is so tough, we were just a little bit on the wrong side of the slopes,' Woods said.
The International team played well, shooting 4 under for a dozen holes – winning on each hole where they made birdie. A bomb by Scott at the par-4 11th sealed the Americans' fate, though Woods and Stricker dug their own graves with a trio of bogeys that cost them three more holes.
Woods and Stricker went undefeated in four matches together at the '09 Presidents Cup at Harding Park. In that quartet of matches, the pair never went more than six holes without registering a birdie. They made none in a dozen holes on Thursday.
The duo was 8 under in two foursomes matches in San Francisco, but was 3 over against Scott and Choi.
Hunter Mahan and David Toms (U.S.) d. Kyung-tae Kim and Y.E. Yang (International), 6 and 5
Mahan and Toms did not play extraordinary golf, but it was good enough.
Mahan and Toms opened with a birdie to take the advantage, winning a half-dozen more holes before closing out the match with a birdie at the par-4 13th.
The American team was 3 under on the round, playing even after birdies on Royal Melbourne's opening trio of holes.
Yang, who complained about the green speeds earlier in the week, failed to get acclimated to the putting surfaces. The longest putt he made was a 9-foot par save to halve the eighth hole.
Phil Mickelson and Jim Furyk (U.S.) d. Retief Goosen and Robert Allenby (International), 4 and 3
Teaming together for the first time in a dozen years, Mickelson and Furyk played like old buddies.
Mickelson and Furyk fell behind after a bogey at the par-3 third hole, but did not lose a hole through the conclusion of the match. The veteran Americans took charge in a 6-hole stretch, winning five times between the seventh and 12th holes.
After the win at the 12th, the Americans halved the final three holes.
Bill Haas and Nick Watney (U.S.) halved with Geoff Ogilvy and Charl Schwartzel (International)
The Internationals took the early advantage, winning two of the first six holes with birdies.
Haas and Watney finally got on the board with a birdie at the ninth hole, their first of the match, when Haas made a 16-footer.
After halving the next four holes, the Internationals won the par-3 14th after Haas was too strong out of the greenside bunker, leading to a bogey.
The Americans rallied, however, with two consecutive wins helped by poor ball-striking by Schwartzel. His drive at the par-5 15th forced Ogivly to lay up, while his approach shot to the 16th was nearly 30 yards off line.
Perhaps rattled by the setting, both sides struggled to halve the final two holes in par and bogey, respectively.
For Haas and Watney, it was quite an escape; the Americans never held the lead in the match.
Dustin Johnson and Matt Kuchar (U.S.) halved with Aaron Baddeley and Jason Day (International)
The last match on the course in the opening session may have been the biggest morale booster for Fred Couples' squad.
Standing 3 down on the 12th tee, Johnson and Kuchar rallied to halve their match with Aussies Baddeley and Day.
All four players were competing in their first Presidents Cup match, and it showed early for the Americans.
After trading birdies at the first two holes, the Americans lost three of the next six. Kuchar, then Johnson, missed par putts from inside 5 feet on the seventh and eighth to fall 3 down.
The Internationals showed their nerves coming down the stretch, losing the 12th after Baddeley thinned a short pitch shot that led to a bogey.
Nevertheless, Day and Baddeley were dormie on the 17th tee. The Internationals took three putts to get down, allowing the Americans to extend the match with a par.
At the final tee, Baddeley followed a solid drive by Kuchar by taking a 3-inch divot with a 3-wood. Unable to advance the ball to the green, Day and Baddeley were forced to try to sink a 30-foot putt to save par and the point. Instead, the Americans made par and a great escape.
Watch wall-to-wall coverage of the Presidents Cup live on Golf Channel. Tournament air times: Golf Channel Thursday 5:30PM-midnight, Friday 3PM-midnight and Saturday 6:30PM-12:30AM. NBC coverage Saturday at 8AM and Sunday at noon. (Note: all times are ET)