美國、英國、加拿大和澳洲的英語，有什麼不同？

They are different in 3 major ways:
1. Use different words but have the same meaning-
Such as " rubbish " (垃圾;廢物) is more British, while " garbage " and " trash " is more US. (Since Canada is in North America, it's more US too.)
2. Different spelling-
Example: " colour " (British) and " color " (US), " centre " (British) and " center " (US).
3. Different pronunciation/different accent-
Example: " today " in British and US is like " to-地 "; but in Australia is like " to-die ".