The Reds full-back produced an eye-catching performance in the national team's opening group game against the USA, but should England face the lottery of spot-kicks later in the competition, Johnson would be happy to take one.
"Every kid dreams of playing for England in the World Cup so it is a dream come true," Johnson told LFC Weekly.
"We hadn't paid too much attention to the tournament during the season because I have had a job to do at Liverpool. I've not been worrying about it too much but once the squad met up we were keen to knuckle down and crack on.
"And I believe you've got to step up to the plate if needed (to take a penalty). I think I've taken three penalties during my career but, if called upon, you need to do it."