A point was awarded for each victory and a half-point goes to each side for a draw.
The winning point came courtesy of Northern Ireland's Stephanie Meadow, 20, who defeated Amy Anderson, 19, of Oxbow, ND, by a 4-and-2 margin, on the par-72, 6,313-yard course.
Britain-Ireland captured the opening three singles matches, including come-from-behind victories from Kelly Tidy, 20, of England, and Amy Boulden, 18, of Wales, who defeated Tubert, 3 and 1.
The morning had started strong for the Americans, with Austin Ernst, 20, of Seneca, SC and Tubert building 2-up leads by the fifth hole over Tidy and Boulden, respectively.
But the tide quickly turned in favor of Britain-Ireland. Tidy knocked in a 25-foot birdie at the par-five seventh to tighten the gap, and both players evened their matches with consecutive birdies at the ninth and 10th. Ernst and Tubert were never able to gain any advantage and fell by 2-and-1 and 3-and-1 margins, respectively.
Lisa McCloskey, 20, of Houston, cruised to a 4-and-3 win over Pamela Pretswell, 23, of Scotland, and temporarily stopped the roll. But Holly Clyburn, 20, of England, tallied the third point with a 3-and-2 victory over Erica Popson, 21, of Davenport, Fla.
The USA's other two victories came from 2010 veteran Tiffany Lua, 21, of Rowland Heights, who edged Bronte Law, 12, of England, 2-up, and Brooke Pancake, 22, of Chattanooga, Tenn., who earned a 6-and-5 triumph over Ireland's Leona Maguire.
After the US came through with a sweep of their foursomes Friday morning, Britain-Ireland battled back with two afternoon four-ball victories, giving the Americans a 4-2 lead after the first day.
Tubert teamed up with Anderson in a four-ball paring for a win. The duo combined for seven birdies during the 4-and-3 triumph over Pretswell and Charley Hull, 16, of England.
Britain-Ireland continued to play well Saturday, capturing two of the day's four-ball matches and split the third to cut the US's lead to 6½-5½ going into Sunday.