Mayday was not used, since it's not required in US Domestic Ops. I simply stated to ATC that I was "Declaring an emergency".
As much as some of us like to believe there is only one way to skin the proverbial aviation cat, the phrase "ICAO standard phraseology" is almost nonsense.
I've flown in Europe, Australia and the US and they all have their quirks and colloquialisms. For example; what the Euros would consider a standard Mayday call would be a debrief item during a sim ride in Australia, as they feel the need to repeat the call sign 3 times, as well. So you see, there's standard RT and then there's standard RT.