The two documents I have that prohibit the use of a power bank in the aircraft / in-flight are both European: EASA and Airbus; I can't find anything from Non-European operators that endorse that prohibition nor can I find anything that says says a similar prohibition is made by the FAA, CASA, CAA, etc.
I have gone through the ICAO and FAA websites / resources but they all refer to size, quantity, risks, actions, etc but none mention use in-flight.
If anyone does have any more resources, it would be appreciated.