I suspect the whole Mayday issue may be because most US pilots and ATCs have English as a first, or at least fluent language. Anyone remember the Avianca 707 that ran out of fuel? ATC only realised they had a problem too late because either the flight crew didn't realise the seriousness of their situation or failed to communicate it. Had the word Mayday been used earlier then they might have been safely on the ground because it is pretty unambiguous.
Europe has a whole mix of languages, so a clear and unambiguous indication of emergency is required in case there's otherwise limited understanding of words outside the routine communication. As English continues its creeping takeover of everywhere except France and Quebec, everyone involved is going to be more comfortable using conversational English.