The friends were at the heart of a dispute that sparked complaints of gamesmanship at Royal Montreal, where the Americans swept four-balls to seize command in quest of a 10th consecutive triumph.
Scheffler and Russell Henley beat Kim and Im Sung-jae 3&2 in the most lopsided day one result.
Kim delivered a fist pump and some trash talk to Scheffler after sinking a 27-foot birdie putt at the par-3 seventh, only for the US star to sink his own 27-foot birdie putt to tie the hole and respond.
"Looked like he poked the bear, from my perspective," Scheffler said.
For Kim, it was good-natured jabbing as they would do in rounds together.
"That's how we play back at home," Kim said.
"It's all fun. I made it on top of him and he gave it to me, and I gave it back. I don't shy away from him. He's a good friend. But at the same time, this week I don't like him. I want to beat him so bad, and I'm sure he feels the same way."
Kim won the eighth hole with a 24-foot birdie putt and was hustled to the ninth tee by Internationals assistant captain Camilo Villegas to avoid a more escalated exchanges with Scheffler.
"There was no reason to stay there and look at him putt. It doesn't help us at all," Kim said. "It wasn't trying to be cheap or do anything like that. We were focused on our own game."
That, however, irked US assistant captain Kevin Kisner, who thought it lacked respect for them to depart before Scheffler's putt.
"They took gamesmanship too far and over the line on sportsmanship and lost some integrity," Kisner told Golf Channel, calling it a "bush league" move.
Scott disappointed
Adam Scott clung to slim hope for an Internationals rally to end a win drought dating to 1998 but the Americans own a 12-1-1 edge in the all-time rivalry.
Scott, the 2013 Masters champion, has never won in 10 prior starts for the non-European squad of global stars and the 44-year-old Australian admitted it would take a stunning fightback to finally breakthrough at Royal Montreal.
"I'm disappointed," Scott said. "We're going to have to find another gear to beat a tough American team.
"It's not over. We're going to have to fight really hard, find that gear, win a session and get going in the right direction."
The Americans have never lost after winning the first session.
"It wasn't a great day," Internationals captain Mike Weir said. "You're down but there's a lot of way to go."
The Americans expect a fightback in Friday's five foursomes matches.
"Those guys are going to come out firing. They are down. They have to come strong," US captain Jim Furyk said. "We'll be ready."
He added: "I don't see complacency. I really don't."
Friday's foursomes matches open with Americans Patrick Cantlay and Xander Schauffele against Japan's Hideki Matsuyama and South Korea's Im Sung-jae followed by Collin Morikawa and Sahith Theegala against Scott and Canada's Taylor Pendrith.
Max Homa and Brian Harman will face Australian Jason Day and south African Christiaan Bezuidenhout, Tony Finau and Wyndham Clark meet Canadians Corey Conners and Mackenzie Hughes and Scheffler joins Henley against An and Kim Si-woo with Tom Kim sitting out for the global squad.