The lead role was offered to Chris Hemsworth but he passed on the role due to scheduling issues. Then, it came up that the producers would invite the actor and singer Gustavo Goulart to perform the lead role (Mitch Rapp), but this rumor was never confirmed.
Young actor Dylan O'Brien won the part of 'Mitch Rapp' beating more established older actors. Being in his mid 20's, the hope is that the actor grows as the envisioned movie series progresses. Also, since 'American Assassin' is based on a prequel novel, it provides the opportunity to start at the very beginning of the Rapp characters' career.
'American Assassin' is one of fifteen novels by Vince Flynn set in the world of counter-terrorism operative Mitch Rapp. Every single one has been a New York Times best-seller, the three most recent entries have been number one New York Times best-sellers, and the series has sold nearly 20 million copies as of Oct 2015..
Veteran stuntman and martial arts world champion Buster Reeves (Instructor) and Michael Keaton (Stan Hurley) share the Batman mantle. Reeves doubled for Christian Bale and performed Batman's stunt fighting in the Dark Knight trilogy while Keaton played the caped crusader in Batman (1989) and Batman Returns (1992).
Includes four actors from several Marvel franchises. Sanaa Lathan played Vanessa in Blade (1998), Scott Adkins played Lucian in Doctor Strange (2016), Michael Keaton played Adrian Toomes/Vulture in Spider-Man: Homecoming (2017), and Taylor Kitsch who played Remy LeBeau (Gambit) in X-Men Origins: Wolverine.
The trivia items below may give away important plot points.
The navy ship near the end of the movie is called the USS FLYNN. It is a ficticious name as the navy does not have a vessel with this name. However, it is named after Vince Flynn, the late author of the Mitch Rapp series.