They have been installed joint third favourites, alongside Ireland, to win the championship and Johnson admits they need restore their flagging self belief as quickly as possible.
"The reaction was expected. We didn't want to lose, especially not in the style we did," he said.
"If you lose the reaction is over-critical and if you win it's too much the other way. We know we didn't do a good enough job as team.
"We need to improve and know that's what we must do. We have to improve as a team.
"We need to build some momentum. We're coming off three losses so we must start the tournament well.
"Italy are coming to Twickenham and there's an expectation that we'll win that game but we'll have to improve on the autumn.
"Our guys have been through a really tough autumn series in terms of results and they need to deal with the disappointment of that.
"We need to react to that and get on with it. We're a more experienced team than four or five months ago."