Pegula went toe-to-toe with Sabalenka early on at Arthur Ashe Stadium but once the Belarusian found her groove there was little she could do to stem the tide.
"She played insane. She played a super-high level," said Pegula, whose win over Sabalenka on grass in June had included a 6-0 third set.
"Maybe that's why she was so pissed off at me," she said with a smile.
Sabalenka's win sent her into a fourth straight U.S. Open final and an eighth consecutive hard-court Grand Slam decider, an Open Era record, stretching back to the 2023 Australian Open.
The defeat leaves Pegula still searching for a first major title. She is the only one of the four semi-finalists yet to win a Grand Slam.
Having lost to Sabalenka at the U.S. Open three years running, Pegula joked that she and her team had even asked Sabalenka's camp not to go so hard on them.
"We're, like, do you like us? Like, we're good people. We're pretty nice to you guys. Do you think that maybe, like, one day she could be maybe off a little bit, so I could just, like, get a chance?" she said.
With Sabalenka in such devastating form Pegula said there was little she could have done to get a different result.
"I'm honestly not that upset, to be honest, because I don't really think there was much I could have done today," the 32-year-old said. "I did my best. I thought I didn't play bad."
Sabalenka, who will surrender the world number one ranking to Elena Rybakina on Monday, hit 29 winners, seven aces and consistently found the lines whenever the American looked to seize control.
"I honestly don't know if she missed a backhand the entire match," said Pegula. "I really want to check."