The Olympics will top an incredible rise for Butland, who finished last season playing in front of 3,000 people on loan at League Two Cheltenham.
"I love big crowds and I love the big stage," said Butland. "It may not have been like that at Cheltenham, but going out and getting games has been a massive part of my development. League Two, even with the long bus journeys and cold showers, was a great grounding.
"I've always felt I'm capable of playing at the top level and that's what I'm aiming for now.
"Just being around the likes of Rooney and Steven Gerrard at the Euros was incredible, and sitting around the dinner table with them for the first couple of days, it was 'wow'.
"Fortunately, I already knew a couple of lads from the Under-21s and I knew Joe Hart from Birmingham.
"He has been a massive help to me and after a couple of days I felt I belonged in the squad.
"I enjoyed putting myself up against Rooney in training and I like to think I made it difficult for the lads to score.
"It was a good test for me and it's something I want more of. I want to be the best in the world."