Romney, the Republican former governor of Massachusetts, sparked widespread criticism in Britain after saying on Wednesday that there were “disconcerting” reports about London’s ability to stage the Games.
Ahead of the opening ceremony on Friday, nine-time Olympic gold medal winner Lewis suggested Romney should have stayed at home.
“Every Olympics is ready, I don’t care whatever he said,” Lewis told Britain’s Independent newspaper.
“I swear, sometimes I think some Americans shouldn’t leave the country. Are you kidding me? Stay home if you don’t know what to say.”
Romney had questioned Britain’s security preparations, and even suggested that the British people were not fully behind the Games.
He later backtracked and said he expected the Olympics to be “highly successful”, but the remarks have hung over a visit that was designed to boost his foreign policy credentials.
Romney, who is attending the opening ceremony, has a keen Olympic eye having stepped in to head the 2002 Winter Games in Salt Lake City after the event was hit by scandal.
But British Prime Minister David Cameron took an apparent swipe at this on Thursday, saying: “Of course it’s easier if you hold an Olympic Games in the middle of nowhere.”
London Mayor Boris Johnson also mocked Romney at a concert in front of 60,000 people.
There was a prickly response in return from the Salt Lake City mayor Ralph Becker, who suggested that Cameron might like to visit them and become more familiar with “nowhere”.