The 25-year-old's £10million summer arrival from Manchester City was greeted with glee on Wearside, but Johnson has struggled to hit the heights on a sustained basis and has lost his place in the international set-up as a result.
Injury prevented his presence in the squad for the World Cup qualifiers against Moldova and Ukraine in September, and he was an unused substitute for the clashes with San Marino and Poland the following month.
But as he battled to make his presence felt at the Stadium of Light, Roy Hodgson overlooked him for the November friendly against Sweden and last week's victory over Brazil, and that is a situation he is determined to address as soon as possible.
Johnson told the Sunderland Echo: "It's always difficult because I have been in the squad for a while and then I have been overlooked for the last couple of games.
"I have just got to get my head down and get better, really. If I do that, then I am confident that I can work my way back into the squad.
"But the key word, in terms of form, is consistency. I think I have only shown tiny glimpses of my best form over the five or six months that I have been here.
"It's difficult for all players - you know it isn't going to be rosy all the time - but you just have to come out the other end of it."