Patrick Cantlay made three birdies and an eagle in his last six holes to give the United States an 8-6 lead after Saturday's four-ball session at the Presidents Cup.
Cantlay's late heroics delivered a 2&1 victory for himself and Sam Burns over Japan's Hideki Matsuyama and South Korean Im Sung-jae and three wins for the Americans in four morning matches at Royal Montreal.
The Americans, who boast 12 of the world's top 25 players, swept five four-ball matches on Thursday before the Internationals equalised by sweeping five Friday foursomes matches.
Four Saturday afternoon foursomes matches will be followed by 12 final singles matches on Sunday.
The Americans, who lead the overall rivalry against the non-European side 12-1-1, seek a 10th consecutive victory while the Internationals hunt their first triumph since 1998.
"Close matches out there. We're still in a good spot," International captain Mike Weir said. "It wasn't ideal but the guys are ready for this afternoon."
Seventh-ranked Matsuyama sank a 24-foot birdie putt at 10 to level the match but the US duo won 11 with a par and ninth-ranked Cantlay eagled from 49 feet to win the par-5 12th for a match-best 2-up lead.
Cantlay birdied from four feet to tie 14, birdied again from 23 feet to tie 15 and sank another birdie putt from just beyond 17 feet to tie 16, matching Im each time to prevent a late charge by the global duo.
At the par-3 17th, Matsuyama missed a birdie putt from just outside seven feet to clinch a US triumph.
Top-ranked Scottie Scheffler and world No 4 Collin Morikawa never trailed in beating Australian Adam Scott and Canada's Taylor Pendrith 2&1.
Scheffler sank his first birdie of the day on a putt from just inside eight feet to win the 16th for a 1-up lead, then made a 16-foot birdie to take the par-3 17th and win the match.
"It wasn't pretty but we did what we needed to do to get the point," said Scheffler.
South Koreans Tom Kim and Kim Si-woo never trailed in beating Keegan Bradley and Wyndham Clark 4&3.
Tom Kim made five birdies, including a 20-footer to tie the 14th, and Kim Si-woo sank a 17-foot birdie putt at 15 to secure the victory.
"It's nice to get things going for the team," Tom Kim said. "We have great chemistry."
Second-ranked Xander Schauffele and Tony Finau lost only one hole and never trailed in beating Canada's Corey Conners and Mackenzie Hughes 3&2.
Conners birdied from 17 feet to win 11 and pull within 1-down but Schauffele sank a three-foot birdie putt to win the par-5 12th and Finau birdied 14 from five feet to give the US duo a 3-up lead.
"You've got to have some dog in you and when I look around my team room, I see a lot of dogs," Schauffele said.
Afternoon foursomes pairings saw the Internationals send out the same eight players who competed in the morning.
Matsuyama and Im were pitted against Scheffler and Russell Henley with Scott and Pendrith facing Max Homa and Brian Harman, Conners and Hughes meeting Morikawa and Burns and Kim and Kim playing Schauffele and Cantlay.