The 22-year-old appeared on track to sneak into Fabio Capello's England squad when he made his debut in the pre-tournament friendly against Mexico after receiving his first international call-up.
But the Manchester City winger was not among the 23 players named and will instead have to watch the tournament from home.
Staying home: Johnson failed to make Capello's final squad for South Africa
'Of course I was a bit down when I got the news and my first thought was that I wish I'd had more of a chance to show what I could do in the two warm-up matches,' he told City's website.
'I would have loved the chance to showcase what I can do on the biggest stage of all but I am not going to dwell on it.
'The England management made it clear to me that I have an international future and I am going to have a rest now and then get my head down and get ready to try and work my way into the side for September qualifiers.
'I suppose if you had mentioned the World Cup to me back in December I would have smiled but I had a thought in the back of my mind when I signed for City that if I did well I might have half a chance.
'I am going to take the positives out of the last two weeks.'
Johnson came into the England reckoning after joining City from Middlesbrough in January, and then dislodging Shaun Wright-Phillips - who is in the World Cup squad - from Roberto Mancini's starting XI.
On the plane: Wright-Phillips made the squad
Johnson's versatility appeared to count in his favour, but he played only six minutes of the friendly against Mexico before remaining on the sidelines throughout the Japan clash.
'I have worked with the squad, I have an England cap which is a wonderful honour and I know that I will be in the mind of the coach and his staff for the future,' Johnson added.
'I am an England fan and in a way I built up so many bonds in the last couple of weeks that I will still feel part of it.
'I have spoken to Shaun (Wright-Phillips), wished him good luck and told him to go and do well. There are certainly no hard feelings towards him.
'I am delighted for Gareth (Barry) too. He has had a great season and it would have been so cruel for injury to have robbed him of a World Cup.
'The lads are fully capable of winning the World Cup. I think we have a great chance along with maybe two or three other sides.
'Of course we will need a bit of luck along the way that goes with winning anything in sport but no one should write off England's chances.'
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