Posted by Mike Dennis on June 25, 2013 at 14:04:51 user MTD.
Most interesting in all of this the language 's' 'z' question. Much simplier to answer than roads and rivers.
In English way back before the Pilgrim Fathers 'z' was the standard usage, so the PMs take this form with them and the USA sticks with it. We in the UK change from the ‘z’ to 's' usage and stick with that.
Take a look at guides to English usage like Fowler and they argue that if you use 'z' forms then are using a superior form of English.
As we all know what everyone means then all is well!