Just as it happens in Spanish, as you have mentioned, there are many different accents within one country, in Chile there are very marked differences between the way people Speak in Arica and those who live in Punta Arenas, not only the accent, but also the words they use. In Santiago skiping school would be "hacer la simarra", but in Rancagua (90 km, south) it is called "hacer la chancha". In santiago people call a kind of bread "marraqueta", but in the south they call it "pan francés" and in some areas in the noth, they call it "pan batido". If you go to Argentina, the way they speak in one region changes drastically from one region to another. In the united states alone there are at least 34 distinctive accents, in Canada about 20 (no taking into account the English spoken in regions that are predominantly French speaking areas), In the UK, the same is true. So, when people say "Canadian accent" or "Australian accent" they really refer to "the most common kind of Canadian and Australian" accents, usually the one you can hear on TV or on the radio.