The Premier League side completed a big-money move for Manchester City's Jack Rodwell on Tuesday, with Billy Jones, Jordi Gomez, Patrick van Aanholt and Costel Pantilimon having already arrived.
Head coach Gus Poyet has spoken of his desire to bring in further recruits, particularly in attack, but Johnson is not worried about the possibility of a settling-in period for the new signings.
"I think from now until the start of the season there will be a big change again - outgoings and ingoings I would imagine," Johnson told The Sunderland Echo.
"But as long as we can keep the basics of what we want to do as a team, I don't think we'll have any problems.
"There's been a lot of talk about different players. We'll have to see who else arrives, but the players who are already here have fitted in quickly.
"I think to be honest, the only reason players don't settle in too quickly is when they can't speak the language. You're a long way away from home and can't understand what is going on."
Poyet led Sunderland to safety last season, as well as a place in the League Cup final, and will be looking to build on those promising foundations when the 2014-15 campaign begins with a trip to West Brom on August 16.
