2013–present: Career in the U.S.
In 2013, Gabel starred as Detective Adam Lucas in the third season of the American medical/crime comedy drama television series, Body of Proof on ABC. His character Adam Lucas was described as young, smart, a rebel and a Philadelphia native, who is a new entrant in the Philadelphia Homicide division. The show was ABC's third most-watched show and yet was cancelled by the channel after the third season. He appeared as Ruan Sternwood in Eran Creevy's action thriller Welcome to the Punch alongside James McAvoy, Mark Strong, and Andrea Riseborough. In the same year, he appeared as a young virologist Andrew Fassbach in World War Z, based on the 2006 novel of the same name by Max Brooks.
Gabel starred as an eccentric computing genius Walter O'Brien on the American drama series Scorpion by Nick Santora on CBS, based on the real life of Walter O'Brien. According to the show creator Nick Santora, "Gabel was able to play the difficulty of expressing emotion while being emotional" for the character of Walter O'Brien, who had difficulty processing and expressing emotions. The series debuted on 22 September 2014 and became the highest rated and highest streamed drama for CBS. Scorpion also won The Golden Nymph award for 'Best Action & Science Fiction TV Series' in Monte-Carlo Television Festival (2018). The series was cancelled after four seasons and 93 episodes, despite having higher ratings than other cancellations with the last airing on 16 April 2018. Gabel starred in all 93 episodes of the series and was termed as one of the "11 Breakout Stars of the Fall TV Season 2014" by TheWrap and TVLine. In the same year, he made an appearance in a crossover episode of Scorpion with American action television series NCIS: Los Angeles.
In Christopher Nolan's science fiction film Interstellar, which premiered on 26 October 2014, Gabel had a small cameo appearance as the administrator who fanboyed over the lead character played by Matthew McConaughey and showed him to his quarters.
In November 2014, he was seen in J. C. Chandor's American crime drama film A Most Violent Year, which was among "323 feature films eligible for the 87th Academy Awards" as announced by the Academy of Motion Picture Arts and Sciences.
A Most Violent Year premiered to great critical acclaim. Gabel played Supporting Lead. Several critics were much impressed by his portrayal of Latin American immigrant Julian, who becomes the sacrificial lamb in a politically motivated barter. In a review of the film, Howard Feinstein stated, "If there were an Oscar for best actor in a single scene, Gabel should win for his mad soliloquy on repentance and despair."
In 2015, he appeared as Adem Qasim, again a Supporting Lead role, in British spy thriller film Spooks: The Greater Good alongside Kit Harington and Jennifer Ehle. He is the primary antagonist of the film, a terrorist who escapes MI5 custody thanks to a traitor in MI5's leadership.
In 2019, Gabel voiced the superhero and Legion of Super-Heroes member Thomas Kallor, also known as Star Boy, in DC Entertainment's direct-to-video animated superhero film Justice League vs. the Fatal Five. Its world premiere was at WonderCon (March 29–31, 2019).
In 2020, he joined the cast of Suspicion on Apple TV+ an eight part thriller series which premiered on 4 February 2022, based on the Israeli TV series False Flag, Gabel portrayed British citizen Sean Tilson alongside Uma Thurman and Kunal Nayyar.