Touted to be the next American star at Signal Iduna Park, Campbell hopes to follow in the footsteps of current USMNT players Gio Reyna and Christian Pulisic, who both broke out with the Bundesliga side as teenagers before establishing themselves on the international stage.
He added: "When I signed with Borussia Dortmund I realized I was following in the footsteps of some great American players like Christian Pulisic and Gio Reyna. They made a great impact at BVB and the USMNT. I am hoping to have the same success."