The midfielder helped Wales reach the semi-finals and is now targeting a place in the Palace side.
Williams, who spent the second half of last season on loan at MK Dons, has returned to pre-season training early in his bid to impress boss Alan Pardew.
"I need to work hard and do my best on the pitch," said the 22-year-old.
"Then it is up to the manager. I love wearing the red and blue."