The hosts won 16½-9½, securing victory with six matches to go and finishing with their best-ever points tally.
Leading 10-6 after the morning foursomes, they needed only 3½ points from 10 singles matches.
Victories for English pair Ashley Chesters and Jimmy Mullen, Cormac Sharvin and a half from Paul Dunne secured GB&I's ninth Walker Cup win.
They have won five of the past six contests at home.
Shropshire's Open Championship hero Chesters, at 26 the oldest member of the team, beat Jordan Niebrugge 3&1 for the first points of the afternoon to earn him three and a half points from a possible four.
Niebrugge lost all three of his matches, two months after finishing sixth at St Andrews in the Open, two shots ahead of Chesters.
Sharvin then beat 52-year-old Mike McCoy 4&3 before Mullen, from Devon, beat Denny McCarthy to become the first GB&I player to have a perfect 4-0 record since Paul Casey and Luke Donald at Nairn in 1999.
"It didn't matter if I won all of my games, as long as the team won. That was the main thing," said Mullen, from Royal North Devon, at Westward Ho. "To win all of my games was just the icing on the cake."
Dunne secured the half-point needed for victory after world number two Maverick McNealy missed a five-foot birdie putt on the 18th.
GB&I captain Nigel Edwards, who led his side to victory for the second time in three attempts, said: "At Royal Aberdeen [in 2011] we were up against it until the death but the boys at the top of the order went out fast as we needed them to do."
Young Irishman Dunne, who led The Open after 54 holes before fading on the final day, added: "I will take winning over 30th place every day. It's so much better to do it as a team. Nigel has been a fantastic captain. He inspired us from start to finish."
Great Britain and Ireland beat the USA to regain amateur golf's Walker Cup at Royal Lytham & St Annes.