The USA are ahead by three going into the final day.
Europe trailed 5-3 going into day two of the 41st Ryder Cup at Hazeltine in Minnesota.
However, after the morning's foursomes, the USA were leading Europe by 6 1/2 to 5 1/2.
Here, we recap how this afternoon's matches unfolded.
McIlroy continued his brilliant form with a 30ft birdie putt at the second and when Pieters drove the green at the 312-yard fifth and holed for eagle.
When both Americans missed short par putts at the eighth Pieters put them three up and another McIlroy birdie saw Europe turn four ahead, although a missed four-footer for birdie at the 11th and back-to-back Johnson's birdies cut the lead by half.
Pieters' back-to-back birdies made it dormie four but Johnson and Koepka birdies kept things alive until the 17th when Pieters' two finally finished them off.
Clarke opted to split up the successful Spanish pairing of Garcia and Cabrera Bello and immediately saw the latter's replacement, former world number one Kaymer, birdie the first.
However, the two-time major winner did not make another until the 15th, which by that stage was only good enough to halve the hole and remain three down.
Garcia managed six birdies, including on the 16th and 17th as he battled to keep the match alive, but Mickelson followed him in on the 17th to seal the win.
Willett flopped one in for a birdie and a half at the second and then sank a 15-footer for birdie and a half at the next.
Westwood's run of three successive birdies from the fifth helped Europe go one up and although JB Holmes cancelled that out at the ninth Westwood celebrated wildly when his long birdie effort dropped at the next.
Holmes' birdie two at the 13th levelled things up again and inexcusably Europe lost the short 17th to a par.
Europe were given two chances to win the last and halve the match but Willett missed from 10 feet before Westwood did the same from just two.
The United States lead Europe 9 1/2 6 1/2 at the end of the second day of the Ryder Cup at Hazeltine.