The Americans rallied from a three-point deficit to tie the score, but McDowell made a clutch birdie putt on the 16th and was conceded his par putt at No. 17. Hunter Mahan missed a chip shot, then missed a last-gasp putt from off the green to save par.
The victory allowed Europe to reclaim the cup won by the Americans at Valhalla two years ago. Rickie Fowler, the 21-year-old U.S. player, gave the Ynaks a shot when he won the final three holes against Edoardo Molinari. Fowler rolled in a 15-foot birdie putt at the 17th to extend the match, then made an 18-footer at the final hole to stun the Italian.
A few minutes later, Zach Johnson bested Padraig Harrington to tie the overall score and leave it in the hands of McDowell, of Ireland, and Mahan.
The Northern Irishman was 3 up with seven holes left. But he made a bogey at No. 12, then an errant tee shot at the 15th, a short par-4, handed Mahan another hole.
With Fowler's half-point, Mahan merely had to halve his match for a 14-14 tie that would've kept the trophy in American hands.
But McDowell rolled in a slick, downhill putt from 15 feet at No. 16 for a brilliant birdie. When Mahan made a mess of the 17th hole, the winner didn't even have to bother with his final putt.
"There was a reason why he was put there," Ian Poulter said of having McDowell in the final spot. "He's the U.S. Open champion. He pulled it off."
McDowell was engulfed by his teammates on the green, but perhaps the biggest cheers were reserved for European captain Colin Montgomerie. One of Europe's greatest Ryder Cup players, he now has a win leading the team in what he called the highlight of his career before it even started.
"We came close," U.S. captain Corey Pavin said, "but we didn't quite get there."
The Europeans started strong, but Pavin backloaded his lineup in the hope of rallying at the end. It almost worked.
Tiger Woods played in the eighth spot and routed Molinari, holing out from the fairway at No. 12 for eagle and playing 15 holes at 9 under. Phil Mickelson, who lost all three of his team matches, played in the 10th spot and beat Peter Hanson 4 and 2.
"No regrets at all," Pavin said. "I'm quite content with everything - except maybe the result."