The hosts needed 13 1/2 points to win the title and took an insurmountable lead after 17-year-old Welshman Rhys Pugh won his singles match against U.S. Amateur champion Kelly Kraft 2 and 1 and Steven Brown halved with Blayne Barber.
Paul Cutler than halved with American Patrick Cantlay in the final match of the biennial event between leading amateur players.
"I'm proud of all the boys," Britain & Ireland captain Nigel Edwards said. "They've all played their part in beating what is a very good American team."
The U.S. team received a letter from former President George W. Bush on the 10th anniversary of the Sept. 11, 2001, terrorist attacks. It was Bush's great-grandfather, George Herbert Walker, who played an instrumental role in the start of the amateur showcase and who donated the cup that bears his name.
U.S. captain Jim Holtgrieve read the letter to the team during its morning meeting.
"As you compete I hope you will reflect on the freedoms you enjoy as Americans," Bush wrote in the letter. "Remember those who have defended your liberties and way of life. I know you will represent the United States with pride and honor."
Holtgrieve said the letter served as inspiration for the team.
"It obviously meant a great deal to the guys in the team room this morning, especially on this day of all days," he said.
But on the course, the home team was simply too strong, as Britain & Ireland wrested back the cup after three consecutive losses.
Britain & Ireland led by five points after the morning foursomes, but the Americans pulled closer after Russell Henley beat Tom Lewis 4 and 2 and Jordan Spieth defeated Andy Sullivan 3 and 2 in the first two singles.
Jack Senior then halved with American Nathan Smith before Michael Stewart earned a full point for the hosts by beating Patrick Rodgers 3 and 2.
Peter Uihlein, Chris Williams and Harris English then all earned points for the Americans, but it wasn't enough as Pugh and Brown secured the victory.
Despite the loss, Spieth said the experience will help him.
"Any time you can represent your country, for me, it's the biggest honor I've ever had," Spieth said. "Being on this team is the biggest honor I've ever had playing golf. ... The crowds, the emotions are higher. The format is different. Peter and I both hope that we can play on a Ryder Cup some day or multiple. I think it's a great step towards it."