In footballing terms, the distance must have felt like light-years, even if Hershey, Pennsylvania, and Dortmund are only a few hours apart by plane. It soon became apparent, however, that Christian Pulisic, a shy, slight boy aged 16, was ready to make the leap -- and more quickly than anyone could have anticipated. Within his first 12 months in Germany, he helped the Black and Yellows win Under-17 and Under-19 championships and broke into Borussia's first XI under coach Thomas Tuchel.
His progress has continued unabated at a turbo-charged pace, smashing records -- the youngest foreign scorer in Bundesliga history, the youngest scorer for the United States, the youngest American to win a major European trophy, to name but three -- like a bull in a china shop.
But perhaps Pulisic's biggest achievement has been to take that incredibly early success in stride, like a seasoned pro who has slowly, gradually and quietly evolved into a top player at some minor outfit off the radar. On top of all his talent, the attacking midfielder is blessed with a level of maturity that belies his 19 years.
If it's true that real greatness manifests itself only in adversity, it might take a little longer before stardom can be ascribed to Monday's birthday boy, for his career trajectory has been that of a sparkling firecracker. There has been no comedown, and none is in sight.
But talk to any Dortmund staffer, and they'll admit that things might have worked out differently ahead of the 2016-17 season. The Westphalians had spent the best part of €100 million on four players, all of whom could play in Pulisic's spot: the three positions behind a central striker.
World Cup winners Mario Götze and André Schürrle, French prodigy Ousmane Dembele and Turkish winger Emre Mor all came with sizeable price tags and reputations. As a barely established first-teamer, Pulisic was expected to take a back seat amongst the fringe players.
He cut a slightly frustrated, impatient figure in August 2016. Tuchel hadn't picked him for the Super Cup against Bayern Munich and left him out of Dortmund's opening two competitive matches, in the league vs. Mainz and in the DFB-Pokal vs. Eintracht Trier.
Would he get enough opportunities in BVB's top-heavy side to expand on his 12 senior outings from the second half of the previous campaign? Pulisic made the squad only after overcoming initial inhibition to play with a sense of freedom in practice sessions, and the tricky prospects for the season ahead threatened to bring back the doubts.
"The confidence that flows from playing more and more games is very important to stay at a high level in this game," he told ESPN FC at the time. "Without confidence, no talent can thrive. The moment you second-guess yourself as an elite player, you're usually in trouble."
Liverpool very nearly took advantage of that moment of uncertainty with a tempting offer to swap the Signal Iduna Park for Anfield, but Dortmund resisted all attempts to enter into negotiations for a transfer. Pulisic got his head down and got on with things, performing with such power and precision at the highest level, including the Champions League, that Tuchel had little choice but to name him as regular starter.
Pulisic became that rarest of players: a young gun who was able to combine natural fearlessness with unerring application and superlative intelligence. No player benefited more from the detailed coaching instructions of the since-departed manager, not even striker Pierre-Emerick Aubameyang, the Bundesliga's leading scorer.
Together with his father, Mark, the U.S. international opted to renew his contract with the Bundesliga giants in January. The decision showed that the Pulisics were not out to maximise income with a hasty move to England but instead preferred to take a long-term view. Borussia have offered the perfect environment to grow for a smart player who recognises the importance of game time above all else.
This season, under the tutelage of new manager Peter Bosz, Pulisic has kept on playing brilliant, dependable stuff in the absence of injured captain Marco Reus, the out-of-sorts Schürrle and Dembele, who was sold to Barcelona. Indeed, German journalists and Dortmund supporters have joked that the Catalans might have bought the wrong BVB winger for €148 million.
But it's not all that funny, and if Pulisic continues to perform at such exalted levels, he will be able to play for any club in the world before too long.