The full-back moved to Germany in January this year, having previously agreed to the transfer as a 16-year-old in 2019. After impressing new head coach Adi Hütter in pre-season, he has taken full advantage of injuries to Ramy Bensebaini and Stefan Lainer to cement his place in the first team.
Despite noting that "everyone is faster, stronger and just overall better players" in the Bundesliga compared to his time in the MLS with New York City FC, Scally has adapted seamlessly to Germany's top flight, playing every minute of all four of his side's league assignments so far in 2021/22.
It seems, then, that everything is going to plan for the 22-time U17 USA youth international. "I chose Borussia because it's a very famous club," he told Gladbach's official website: "It's a very traditional family loving club and I knew this was a place I could get my game to the next level."
There is little doubting that he has already done that. After all, how many defenders can say they have thrived on their Bundesliga debuts, and against none other than Bayern Munich?
Scally helped keep Leroy Sane and Co at bay in that Matchday 1 encounter, with the Foals earning a 1-1 draw against the defending champions, and the game is understandably not one he will forget in a hurry.
"My best moment so far was against Bayern when we got a point," he said. "It was my first Bundesliga game. It was just a really good game overall.
"The atmosphere on my home debut was crazy. I'd never played in front of a crowd like that, and to think it was only half full… And when the crowd started singing my name - it was like a dream!"
Robust in defence - Scally's tally of 43 challenges won puts him in the top 25 Bundesliga players this term - and a threat going forward - his five shots and eight crosses from open play to date are among the best numbers for defenders - the New York native is already posting returns to rival those of seasoned pros.
And he has done so playing in both full-back positions, originally on the left in Bensebaini's absence before switching to the right to cover for the injured Lainer. "I'd say [I prefer] right-back because it's my normal position, but I also like left-back a lot."
It has not gone unnoticed by the club's fans, who, in addition to adding his name to their matchday chorus, also voted him as Gladbach's Player of the Month for August. "It's like a dream come true," he said of the prize. "I just hope better things come the next month."
A trip to 17th-placed Augsburg and a home clash with Borussia Dortmund - teeing up a showdown with childhood friend and compatriot Gio Reyna - suggest Scally will continue to go form strength to strength.