The Leeds Rhinos player helped the youngsters to a famous 14-8 victory over their revered international foes on Saturday.
They will attempt to complete a 2-0 series whitewash – achieved just once before, in 2002 – when the sides meet again at Emerald Headingley on Friday.
“It hasn’t really sunk in yet; to defeat Australia is a massive achievement,” said Johnson.
“They were very strong, a big physical squad and some of their middles were huge compared to us.
“However, I thought our middles matched them well.
“Harry Smith kicked very well and we were able to build pressure on their full-back.
“They will be even tougher for us this week and desperate to try to get one over us at Emerald Headingley on Friday.”
Johnson, who only signed for Rhinos from Castleford amateurs Lock Lane 12 months ago, added: “It will be unreal to be stood there singing the national anthem at my home ground.
“Hopefully I will get picked and to do it again would be amazing.
“It has been a great year for me personally.
“I was able to get some game-time with the Under-19s early in the season when our skipper Harvey Whiteley was injured, which meant I had to do big minutes and that has helped me massively.”
Johnson missed just two games all season after converting from a half-back to hooker, running in 14 tries in 24 appearances, form that saw him sign a new deal in July that runs until the end of 2022.