Thern, part of the third-place team at the 1994 World Cup, branded those who believed England played well in Monday's opening 1-1 Group D draw against France as deluded.
Sweden lost their first game against Ukraine 2-1 but Thern, one of Betfair's football ambassadors for Euro 2012, said: "Apparently the one shot towards the France goal over 90 minutes was all it took to ignite the chronic English illusion of world football supremacy.
"I said before the Euro finals started that Sweden would beat England and I stand by that statement despite the horrific display against the Ukraine."
England have never beaten Sweden in seven tournament clashes and Thern, who won two and drew two of his four matches against them, added: "England's performance had none of the quality they like to boast it had.
"France had 15 shots on goal compared to England's one.
"Their style of play does not intimidate as it is predictable and stereotyped.
"England has historically struggled against Sweden as they cannot capitalise on our strength, which is the physical game.
"Sweden does not fear this style of football in ways that other teams do.
"The only thing that could have been better for the Swedish team would have been if the manager position had been handed to somebody other than Roy (Hodgson) as he is a very competent manager with substantial international experience."