Dialects - a musing

Just had a shower and was musing how differing countries have differing languages and dialects.  The main muse is English Speaking countries but will muse on other languages later.

USA - origins of language was European, UK and Ireland.  The american English language is very different from others.  And there are many dialects (Californian, Texan, and South Eastern states, etc)

Australia - as above for USA, European, UK and Irish.  Unlike USA there are very few dialects but as for USA, a distinctive twang.

New Zealand  - also like USA and Australia, the origins are European, UK and Irish (with Maori to provide a richness of language).  As with Australia there are very few dialects (except lower South Island or seperate iwi)

The UK is blessed with a long time having their language to bloom but amazingly there are many local dialects (Jordy, Scouser, Cockney et al)  Oddly enough none of those dialects are evident in the colonies.

Now the others.  There are five European countries with languages in colonies around the world. From memory and dealing with people from those countries.  They are French, German, Portuguese, Dutch and Spanish.  All four sound very much like their parent country.

You have to remember most of the above countries have had between 400 to 200 to harness their dialects.

But there is also a burning question raised by this??  How did the above countries  (USA, Australia, and New Zealand) get to have very distinctive dialects from each other?  All had the same birth from mother countries, with same people?  The only real answer is Mother Nature and local environment.  That's my thought!!