The 19-year-old has been named in Chris Coleman's squad for the forthcoming World Cup qualifiers against Scotland and Croatia.
Williams, who has impressed for Palace in the Championship this season, has said that featuring for his country would be a "great honour".
"I don't think you can beat that achievement, it would be a dream come true," Sky Sports News quotes him as saying.
"I've played over 40 games in the Wales youth system so it would be a great honour to make that debut.
"I haven't played a first-team game yet but I've trained with [Gareth] Bale and [Craig] Bellamy and [Aaron] Ramsey and it's been a great experience, so I'm excited to do it again."
Wales face Scotland at Hampden Park on March 22.