According to a Flyaway Trip contest for the Justice League premiere from radio station Jam’n 94.5 through iHeartRadio, the first American premiere for Justice League will be on Monday, November 13th in Los Angeles.
The contest confirms the following information within their description of the giveaway:
Justice League Movie Premiere Flyaway Trip to L.A.
Enter to win a trip to Los Angeles for the premiere of Justice League starring Ben Affleck! You and a guest will fly to LA, spend two nights in a hotel and attend the premiere on November 13.
No other official outlets or anyone attached to the film has confirmed this date, but it doesn’t seem like the source of the information is one to truly question or the date of the premiere is questionable in itself, as it’s within the same week of the film’s release on Friday, November 17th.