The Irish captain and centre paid tribute to England's spectacular five-try display which secured the first Grand Slam under the reign of head coach Clive Woodward.
But he insisted it was formidable defence as much as fabulous tries which sealed the 42-6 triumph at Lansdowne Road.
"Their scrambling defence is excellent," said O'Driscoll. "It really killed us. It is one of their great strengths and one of the best you'lll come across.
"They get their big guys around the rucks and their fastest players out wide and their organisation is fantastic. They have been perfecting it for quite a few years and they all know exactly what to do."
O'Driscoll, whose side were powerless to stop England scoring five tries in the RBS 6 Nations decider - two from Will Greenwood and one each from Lawrence Dallaglio, Mike Tindall and Dan Luger - also conceded that England deserve to be considered the best team on the planet.
"We gave everything we had and tried hard but they proved why they are the number one side in the world," said O'Driscoll.
"We were struggling at first with the tempo of the game. It was very fast, the quickest I've played in the 6 Nations."