"We only had one conversation with him on the phone," Defoe said.
"Up until then I had played a full season with Tottenham. It was a quick conversation, 'You are not included'.
"I was scoring goals, so maybe I felt like I had done enough to still go to the tournament, but obviously it was not meant to be.
"It was a hard phone call to accept because I felt in my heart I did enough to get on the plane."
Former Tottenham Hotspur star Defoe admits his decision to leave North America for a Premier League return was motivated by his desire to again play for his country.
He added: "I sat back (in Toronto) and thought if I have still got that ambition to play for England I need to be playing in the Premier League again.
"That was probably behind my decision to come back."
Since joining the Black Cats from Toronto, 34-year-old Defoe has scored 36 goals in 84 appearances in all competitions, including tallying 14 times in 28 Premier League matches this term.