The whole “declaring an emergency” seems to be one of those American things.
“Mayday Mayday Mayday.....(details)”
“Are you declaring an emergency?”
“Wilco (sic) we are, roll the trucks”
Company policy where I work is that the decision to use the P or the M word is at the discretion of the PIC. For example I have had to do a flap zero landing into a CTAF with a long runway and made neither call because LDR was much less than that available, and actually the aircraft can be operated with the flap system MEL as long as everywhere is long enough. Whereas a Flap Zero Landing into an airport where you had to defactor the landing distance in order to get in requires a call, as would a flap zero caused by a hydraulic failure.