The 23-year old German-born American came on for the final 20 minutes of the USA's 1-0 defeat to France in Paris and was buoyed after the match.
"It was exciting. I was happy to get a few minutes, and hopefully there are more to come," he said.
"Of course it's nice to get your first cap, but I hope that next time we are going to win."
Johnson represented Germany at U10, U20 and U21 levels but made the switch to the USA recently which has now paid off with a debut international appearance.