It could be argued that only native speakers of English from England are true native speakers. Other countries that have adopted English as their primary language (America, Australia, Canada) have cultural and language differences, spelling, pronunciation etc.
One's country of origin has less to do today with the language one is brought up to speak as one's first language than ever before in history. Thus, if one is brought up to speak English as one's first language, then that person is a native speaker of English -- with all of its wonderful regional variants.
All over the world there are countries where the native language is English.
You can look the list here
The English language is almost the same, If you understand English from London, You can understand the English of Australian native speaker too (and everyone speaks English).
There are a bit of differences in every type of English, like slang, accent and some words.
Example: In American a lot of people use "What's up", In England almost nobody does it. In American everyone says "color", in British "colour".
I can't explain every differences, You can search on Google
Difference between english and [other english language, like Scottish etc.] for get a lot of differences between English and other types of English.
I link you this article "What Are The Differences Between American And British English?"
But in the web you can found more thing about it!