An exemplary system directs a camera included within a mobile device to capture a video feed, directs the mobile device to display the video feed within a display screen of the mobile device, and identifies a plurality of adjacent pixel blocks within the display screen that have signal characteristics that uniformly vary by more than a threshold amount over a predetermined time period. Based on the uniformly varying signal characteristics, the system determines that a pixel region constituted by the pixel blocks corresponds to a position of a display device within a field of view of the camera. The system identifies a media content instance being displayed by the display device, identifies augmented reality content associated with the media content instance, and directs the mobile device to display the augmented reality content within the pixel region of the display screen.