Not sure what year your trailer is but on my 2016 there are 2 USB jacks in a black bezel mounted in the face of the white cabinet that holds the BDP - they are power only, just like the USB plugs back in the bedroom on either side of the queen bed. There is also a USB jack on a short cable laying on top of the BDP box - that is an audio input to the Clarion head unit.
To hook a video device up you need to get an HDMI switch and connect both the BDP and your Apple TV to its inputs and its output to the cable that was connected to the BDP. The video & audio will be routed to the TV and the audio back to the stereo via the TV, just like the blu-ray.
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Keith & Barb
2016 30' Flying Cloud
2016 Ram 2500 diesel
Southeastern Camping Unit, WBCCI #1675