Williams scored in the 2-1 defeat of England in last night's Berlin final.
Afterwards, the youngster said: "I just wanted the match to end there and then.
"It has been an incredible year for me, I will never forget this. All footballers dream of moments like this and I have fought hard to be here and so has my family to be able to experience this together. This is for everyone who believed in me from the start.
"This is a unique team, we are all going in the same direction. We are very happy with this victory and since the group stage we have won all the matches and are ready for the next challenge.
"First of all, we have to enjoy having won the EC. We have to take it step by step then, there are two years left until the WC. It is two long years and we will try to prepare for it but we will take it step by step."
Williams has a contract with Athletic to 2027.
"I always try to do my best to help the team. It is true that people are getting to know me and respect me and I appreciate that respect very much. That's what I work for every day and I hope I can be one of the best in my position," he said.
Williams concluded by paying tribute to his Spain teammate - 17-year-old Lamine Yamal, of Barcelona.
"Lamine is incredible. You all have seen him in the tournament. He has been awarded the best young player of the tournament and I don't think there are any limits to him (on how far he can go). In addition to being a great player, he is also an incredible person."