Williams, a product of Palace's youth academy, has been included in the Wales squad before but is yet to make his senior bow for his country.
The 19-year-old has been promoted from the Under-21s for the upcoming World Cup qualifying double-header against Scotland and Croatia.
He says featuring for his country would be "a great honour" after impressing for Palace as they push for promotion to the Premier League this season.
"I don't think you can beat that achievement, it would be a dream come true," he said.
"I've played over 40 games in the Wales youth system so it would be a great honour to make that debut."
Williams is looking forward to being in the Wales camp and potentially playing alongside the likes of Gareth Bale, Craig Bellamy and Aaron Ramsey after training with them in the past.
The teenager added: "I haven't played a first-team game yet but I've trained with Bale and Bellamy and Ramsey and it's been a great experience, so I'm excited to do it again.
"They've all played at the top level for the top clubs and you see how professional they are in training and it shows in the games and their performances."
He reserved particular praise for in-form winger Bale, who has been Tottenham's star man this season, scoring 21 goals in all competitions.
Williams added: "He's very special, Bale. I think probably one of the best in the world right now. And he's very important for Wales to be successful."
Interview courtesy of New Era Global Sports.