This is perhaps my favorite word in Vietnamese, and not because I'm American. For some reason I find it funny that the Vietnamese word for "United States of America" is Mỹ.
That's it. Four words reduced to two letters.
It's my favorite word because it's so fun to say. Every day I am asked multiple times where I am from. It's one of the few words I can say in Vietnamese so I use it.
The "M" sound is exaggerated. To my ears it sounds more like a "b" than an "m", which is not terribly surprising since the letters are formed the same way by the lips. The "y" is pronounced like the "ee" sound in English.
The tilde over the vowel indicates that it is pronounced with the "tumbling tone". The symbol is actually a pretty decent illustration of how to pronounce it. The tone starts normally, dips and then rises sharply to finish at a tone higher than where it started. It's spoken almost as if it's a question.
(This is not to be confused with the "asking tone", which would be Mỷ. This starts lower than normal, then rises back to normal. Understand? No, neither do I. To western ears they sound very much the same. Vietnamese is the hardest language I have tried to learn, mostly because of the six tones, one more than Chinese, two more than Thai.)
The question I get, then, is "Where you from?"
The answer, if I were to spell it in phonetic English, is "Me?!" As if someone has accused me of a particularly heinous crime and I am responding in surprise and alarm.