Ramsay-Peaty is the greatest breaststroker of all time, having gone eight years unbeaten in the 100m and holding the world record in that event and the 50m.
He was the defending Commonwealth champion in the 50m and decided to continue in the sport because it was added to the 2028 Olympic schedule.
On Saturday he suggested the shorter distance would provide his best chance of a medal in Los Angeles, given his age.
“I thought I could have done better there,” Ramsay-Peaty said after finishing in 26.94 seconds – 0.44secs behind Williamson.
“It is quite disappointing in terms of the time, and, as we know, times equal medals.
“I felt I could have been a little quicker, but I need to look at it and see what is going on because nothing makes sense this week to be honest.”
Ramsay-Peaty dominated the events under the coaching of Mel Marshall, who relocated to Australia in 2024.
After the Paris 2024 Olympics, Ramsay-Peaty began training at Repton in Derbyshire but has since moved back to London to the tutelage of Lisa Bates.
“I am very, very happy, couldn’t be happier with where I am training now,” said Ramsay-Peaty.
“It is hard work, but we need to make sure that hard work is going in the right place.
“These things don’t happen in three months; they happen in two years and we need to make sure we keep investing.”
Meanwhile, there was gold for England’s Brock Whiston in the women’s 200m breaststroke SB8 final, with 15-year-old team-mate Iona Winnifrith taking bronze.
Amalie Smith, 16, took silver in the women’s 200m individual medley final, and the England quartet of Freya Colbert, Abbie Wood, Leah Schlosshan and Freya Anderson won silver in the women’s 4x200m freestyle relay.
