Standard RT
As a European PPL we have learned the priority between different types of R/T communication, where ‘Mayday’ have the highest priority, and ‘Pan Pan’ have the second highest priority.
A European PPL could in principle be flying in US airspace without knowing that he is expected to back off when the world ‘Emergency’ is used.
It is important that we all use the same standard ICAO Phraseology, whatever that is.