Johannsson was born in Mobile, Alabama, and his family moved to Iceland when he was three years old.
The 22-year-old forward plays for AZ Alkmaar in the Netherlands after making his name with Aarhus in Denmark.
"We are obviously very thrilled for Aron," former Germany striker and coach Klinsmann said. "It's an exciting time for him. He's done a great job in these couple days getting to know the guys.
"Hopefully if the game goes well tomorrow night, there will be a chance for him to make his debut with the U.S. National Team."
Klinsmann, who has been keen to attract dual-nationality players to his team, could also hand a first start to Germany-born John Anthony Brooks who plays central defender for Hertha Berlin.
FIFA rules allow players eligible for more than one country to make a single change of allegiance, so long as they have not played in a competitive game for a full national team.
(Reporting by Simon Evans in Miami; Editing by Frank Pingue)
