The former Fulham forward has become a regular part of Juergen Klinsmann's US national team and is in the squad for Friday's World Cup qualifier against Costa Rica in Denver.
A move back to the States a year ago, when he joined Major League Soccer's Seattle Sounders has reignited a career which had badly lost its way after he moved to England as one of America's most highly-rated young talents.
"I went over in 2008 in the MLS off-season in January, so I had to play catch-up," Johnson told Reuters.
"Fulham were near the bottom of the table, fighting relegation so for an American player to come off his off-season into the biggest league in the world, with the most pressure, it was a big-time transition.
"It took me a long time to adapt. I got my chances but when I got them I wasn't 100 per cent sharp. I wasn't confident. You get a few chances over there but if you don't deliver, the next person comes in and replaces you."
Fulham loaned Johnson to Cardiff City, Greek team Aris Salonika and Preston North End, but the goals just never came for the Floridian.
"Given more time, if I was in better shape when I came over, it could have been a different experience," he said. "But when you don't have confidence, you start second-guessing your own ability."
Seattle Sounders coach Sigi Schmid believed Johnson was capable of re-finding the form he had shown with Kansas City before his move to Fulham, and gave him a chance, which the forward has made the most of.
Last season he struck 14 goals in 24 starts for the Sounders, quickly becoming a favourite with the fans of MLS's best supported team who average over 40,000 fans per game.
He may have become a forgotten man in London but in Seattle he is a well-known personality in a city where soccer is truly mainstream and he enjoys the attention.
"This is what we have all wanted and dreamed of, one day to have a professional soccer league here where we get the recognition that the basketball players and football players get - it feels really good," he said.
That mood has been helped by his return to the US national team and in his first international in over two years, he scored both goals in the 2-1 qualifying win over Antigua.
Klinsmann has highlighted Johnson's pace and ability to run at players as his main asset and he has used him, at times, wide on the left, but the former Germany coach has been impressed by the striker's hunger.
"We see a player that is extremely proud to be back in this group. We see a player that has matured a lot and knows now he has a point to prove," the coach said after the Antigua win.
Klinsmann has a number of options in attack with Jozy Altidore in prolific scoring form for AZ Alkmaar, Tottenham forward Clint Dempsey and Herculez Gomez, who continues to impress with Santos Laguna in Mexico.
But he clearly has a soft spot for Johnson who, even if he might find it hard to keep a starting slot throughout the World Cup qualifiers, is a strong option from the bench.
Despite his disappointing time in English football, Johnson also holds out the hope that he might get another opportunity to show his value in a top European league.
"Hopefully, I'm 28, World Cup coming up. I've fought my way back into the national team.
"I just want to be the best I can be for the Sounders and if I am doing that, I will get the national team call ups and take advantage of those opportunities," he said. "I've still got some years ahead of me. I feel like I'm still 21".
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- Juergen Klinsmann