In Australian English, they are saying "mate", not mike. Mate is a friendly term.
As far as dialects go, there are so many even within each country it's hard to say. I'm a native English speaker from America, but I can fully understand people from UK, Australia, Ireland, Scotland, etc.
In America, there are several different dialects. I'm a Texan and have been all my life. Most of my family has a distinctive accent, but I, for some reason, do not. I'm pretty good at imitating accents though. :-)