The Bulgarian Football Federation are currently being investigated by UEFA after their fans allegedly racially abused England players during their qualifier in September.
"I haven't given it a minute's thought, it's not something I'm worried about," said Williams.
"We've worked hard in the UK to kick it out and I haven't received anything [racist chanting] really in the last few years.
Bulgaria seems to be a country that it's still there knocking about, a bit of racism, so hopefully they can kick it out as well."
Wales can not qualify for next year's finals, but they can still finish third in Group G if results go their way on Tuesday.