The 24-year-old, who is currently playing in the Premier League, told the BBC’s Newsnight programme he had never been happier than he was in the World Cup.
“I was really excited when I got here, but it was tough to get the team going.”
There was a bit of an atmosphere at the end of the tournament, but we were winning all the time, so we were just happy and it was a nice experience.
“Mr Lusby added: “I think I have grown a lot since then, and I’ve learnt a lot.
“I’ve got a lot of good friends now, so I’ve got good connections.”
Mr Williams, who plays for Newcastle United, said he was “very proud” of his team’s performance, but also “very humbled” by the players’ reactions.
“We’ve been training really hard,” he said.
“We’ve just got to go out there and get it done and it will be great for us.”
Watch Newsnight on BBC One at 23:30 GMT on Saturday and the BBC Sport website from 20:30 on Sunday.
Follow our live blog of the World Championships here