Wales face Group D leaders Serbia in a World Cup qualifier at Cardiff City Stadium on Saturday.
Williams, 23, on loan at Ipswich Town from Crystal Palace, was an unused substitute in the 6-1 World Cup qualifying defeat in Novi Sad in 2012.
"We haven't really spoken much about it this campaign," said Williams, who has 17 caps.
"It's a long way behind us and we've come so far as a team and what we have achieved since then has been amazing.
"It's the same players and what they've created here is something really special."
Defeat in Novi Sad was as a fourth successive loss for Chris Coleman, the worst start by any Wales manager.
But Coleman oversaw a change in the national team's fortunes and, in qualifying for Euro 2016, Wales reached their first major tournament for 58 years.
Williams has returned to the Wales squad after missing the opening three games of the World Cup qualifying campaign after injuring an ankle during pre-season.
Serbia are top of Group D with seven points from their first three matches, while Wales are two points behind in third place having won one and drawn two.
Midfielder Jonny Williams insists Wales have come a long way since their heavy defeat in Serbia four years ago.