Phil Mickelson (Getty Images)
The home side held a 3 ½ - 2 ½ lead over the International team after the first day and extended that when Phil Mickelson and Keegan Bradley won the top match 4 and 3 against Jason Day and Graham DeLaet.
But just moments later Ernie Els and Brendon de Jonge beat Bill Haas and Hunter Mahan by the same score to reduce the deficit.
A long rain delay, though, means that the other four matches on course
will have to be completed when play resumes at 7.35am local time on Saturday morning with both teams up in two.
Mickelson and Bradley lost the opening hole after Day and DeLaet recorded a birdie three, but then hit back in style by winning four consecutive holes from the fifth - all of them with birdies.
That put the American duo three up after eight and Mickelson could have increased that lead on the ninth but saw his birdie putt come up just short as the hole was halved.
That group were
on the tenth when the teams were forced off the course but that did not knock the Americans off their stride as they won the hole with a par
upon returning and recorded further wins on
11 and 12 to go dormie
Day and DeLaet rallied to win the next two but a half on 15 secured victory for the Americans.
Els and De Jonge were three up after nine against Haas and Mahan after winning the second, third and fifth holes with two birdies and an eagle.
When they returned after the break, the duo claimed a birdie on 11 and halved out the rest to win.
Steve Stricker and Jordan Spieth were one up on Branden Grace and Richard Sterne after seven when the rain came, although the South African pair had trailed by two before winning the sixth with a par.
Birdies at eight, ten and 12 saw the Americans surge out to a four up lead before the Europeans clawed a hole back on 13.
The 14th was then halved before the players picked up on 15 in dwindling light with the Americans three up.
Tiger Woods and Matt Kuchar will be the favourites to wrap up victory in their match on Sunday morning as they went three up with six to play.
A birdie on the first saw them move ahead of Louis Oosthuizen and Charl Schwartzel and they went two up with a further birdie on the sixth.
The South African duo picked up a hole on eight but the Americans hit back on nine and then a bogey on 12 extended their lead further.
Hideki Matsuyama and Adam Scott held the upper hand in their match and were four up through 11 against Jason Dufner and Zach Johnson.
Matsuyama and Masters Tournament champion Scott were leading by two after five and extended that lead to three on the sixth when returning after the rain break.
The Americans won the seventh with a birdie but pars on eight and 11 were enough to put the international duo in a commanding position.
Webb Simpson and Brandt Snedeker were all square against Angel Cabrera and Marc Leishman at the rain break but had established a one up lead by the end of the day.
A par on 11 and a birdie on 12 had them two up but Cabrera and Leishman picked one back up at 13 before play was stopped.