Taylor Fritz believes he "let a lot of people down" after failing in his dream to become the first American man in 21 years to capture a Grand Slam title.
Fritz was outclassed by world No 1 Jannik Sinner 6-3, 6-4, 7-5 in Sunday's US Open final.
Andy Roddick, in New York in 2003, remains the last US man to win a Grand Slam title.
"I'm pretty upset with how I played. I feel like I almost let a lot of people down," admitted the 26-year-old Fritz.
"I'm pretty just disappointed in how I played, how I hit certain shots. It sucks.
"I just would have liked to have played better and given myself a better chance. It's really disappointing right now. I feel like American fans have been wanting a men's champion for a long time."
Fritz was always chasing Sunday's final, even being broken when he served for the third set as Sinner went on to claim his second Grand Slam of the year after his maiden triumph in Australia.
Fritz was the US first man since Roddick at Wimbledon in 2009 to reach a Grand Slam final, seeing off higher-ranked former runners-up Casper Ruud and Alexander Zverev on the way.
The world number 12 had defeated Sinner in their first meeting at Indian Wells in 2021 before the Italian avenged that loss back in the Calfornia desert two years later.
"The serve and the movement, massive improvements," said Fritz when asked to pinpoint the changes in Sinner's game.
"I felt in 2021 I could get myself in points off of his first serve every time. Then it was much easier to hurt him from the ground, as well.
"So he's much faster, a lot better out of the corners. His serve is really good now."