"You kind of want to send a message a little bit," Kobe Bryant said. "This was the second game in a row that a team has played us close. We didn't want to give them confidence."
The Americans (5-0) will play Australia (3-2) in a quarterfinal game Wednesday.
LeBron James added 18 points, getting the Americans' first seven of the third quarter before Durant took over. Chris Paul scored 17.
"We're a great shooting team, but in close games sometimes you've got to go down and get some easy ones," James said. "Once you get a couple easy ones at the rim, then the three-pointers open up and you saw what KD was able to do."
Two nights after surviving their first real test in a 99-94 victory over Lithuania, it seemed the Americans might be headed for another tight finish. Argentina shot 56 percent in the first half and trailed the United States, 60-59, at the break.
Minutes into the second half, the game was effectively over.
Durant's three after James' surge gave the United States 10 points in the opening 2 minutes, 10 seconds, and he made back-to-back three-pointers midway through the period to make it 85-68.
Durant, who holds the U.S. scoring record with 38 points in the 2010 world championships, might have threatened that mark if not for the lopsided score. He checked out for good about a minute into the fourth quarter.
Manu Ginobili scored 16 points for Argentina (3-2), which would have won Group A via a tiebreaker if it had blown out the U.S.
Instead, the Argentines finished third and will face Brazil in the quarterfinals.
The Americans, who insist their defense is their strength, allowed Argentina to make 11 of its first 15 shots, falling behind, 30-29, when Leonardo Gutierrez made a three-pointer with 1:03 left in the first quarter. Durant's trey as time expired gave the United States a 34-32 lead heading into the second period.
The United States has two days to work on its defense before facing the Australians, who pulled a surprise earlier Monday, handing Group B champion Russia its first loss, 82-80, on Patty Mills' three-pointer as time expired.
Then again, considering their offensive firepower, maybe the Americans' defense is fine as it is.
Durant finished 8 of 10 from three-point range and the Americans connected on 20 of 39 as a team from beyond the arc.
James, who scored nine of his 20 points in the final four minutes Saturday against Lithuania, now has 225 points as a U.S. Olympian. The reigning NBA most valuable player pulled within six points of Charles Barkley for third place on the U.S. career list.