Englishman Willett, the Masters champion, had distanced himself from brother Peter's blog in the run-up to the match at Minnesota's Hazeltine National which labelled some American fans "a baying mob of imbeciles".
But after a weekend of raucous support for the home side who reclaimed the trophy 17-11, rookie Willett changed his tune.
"Unfortunately some American fans showed that @P_J_Willett was in fact correct," he said on Twitter.
"Still shows that sometimes fans don't know when to call it a day...Shame really."
Willett had a forgettable Ryder Cup debut, failing to win a point and in Sunday's singles was thrashed 5&4 by Brooks Koepka.
While the majority of American fans stayed within the bounds of fairness, despite being extremely loud, some of the heckling edged over the line.
Northern Ireland's Rory McIlroy was targetted on Saturday and asked for one fan to be removed.
"At times it went a little bit too far," he said. "But that's to be expected when you are teeing off at 7:45 in the morning, you're seeing people on the first tee with a beer and matches aren't finishing until 4:30, 5:00.
"A couple of people crossed the line but we'll take it on the chin."
(Reporting by Martyn Herman in London; editing by Amlan Chakraborty)
