As the 19-year-old has yet to be capped by Wales, he is theoretically still eligible to represent England,
But there will be no late change of heart and he is looking forward to making his bow in front of his Welsh father Peter during the upcoming World Cup qualifiers against Scotland and Croatia.
"I haven't heard anything personally from England and have not had any second thoughts about it, because Wales have given me my chance and I've enjoyed every minute," he said.
"I'm just looking forward to making my debut. I've been part of the Welsh set-up a long time now. I think I've played about 40 times for the different age-grade teams so it's been a long journey, but a great one as well and Osian Roberts and Bran Flynn and have really helped.
"I was born in England, but Wales chose me to play for them from a young age and I chose to play for them.
"It's exciting and not really sunk in. My father is also definitely going to be there - he travels everywhere to watch me play.
"I'm trying to take it in my stride. I know it would be an unbelievable achievement."
Williams has been on Wales' radar for some time, while England were also interested in him pulling on a Three Lions shirt, having been born in Kent.
His development was stopped in his tracks when he suffered a broken leg while playing for Wales Under-21s against Armenia in November 2011.
But the teenager was inspired by how Arsenal midfielder and now Wales colleague Aaron Ramsey fought back from his own horror injury in 2010 to rediscover his best form for club and country.
He said: "One of the things I thought about when I was recovering was Aaron Ramsey, as he was someone who was also part of the Wales set-up.
"He sent me a really nice text which was really unexpected and great to see. I saved it and it's great now to be back and part of the same squad again.
"It was really nice and good advice and I spoke to him when I was coming back and it was great to have that person around during that time.
"It would be a dream to play alongside him. I remember watching him when I was younger and still remember that goal he scored against Scotland (in a 3-0 win in 2009) so if he can do that again on Friday that would be brilliant."