Defoe left Tottenham to join Toronto FC and concerns were raised that the striker might be overlooked by England boss Roy Hodgson after departing the Premier League, just a few months before this summer's tournament.
David Beckham has proved that a player can remain in contention after moving across the Atlantic and Defoe believes he will stay in Hodgson's plans if he scores regularly.
"Obviously it's at the back of my mind, but first and foremost it's important to concentrate on your club and make sure your form is good," said the 31-year-old.
"As a forward you get judged on scoring goals. I think that's on my mind first and foremost, and then see what happens with the World Cup."
Toronto boss Ryan Nelsen worked hard to land the signing of his former Tottenham team-mate and is expected to hand him a debut on Saturday against Seattle Sounders.
Nelsen dismissed suggestions that Defoe will find it difficult to impress Hodgson in the MLS and insists his finishing skills are well respected by the England boss.
Asked if Defoe could be out of sight and mind, Nelsen replied "No, not at all. You know a lot of conversations have been had behind the scenes with certain people.
"When you are a player like Jermain, the manager knows Jermain inside and out, everybody does, they know what he's going to give them. As long as he's fit and playing well, he'll be up for selection."
Defoe will be reunited with some familiar faces when Tottenham arrive in Toronto for a July friendly.
"I spoke to a few of the players, they are looking forward to that," said Defoe.
"Yeah it will be strange but you know that's a fixture that I'm looking forward to."