Wildrover said that AmE is not English
Then he is wrong and I hate saying this being British, but American English is more like the traditional English as it was, because GB English has developed over the years.
For example in GB English we have dropped the 'z' and replaced it with a 's', providing a more softer pronunciation.
In some ways, American English is more like the English of Shakespeare than modern British English is. Some expressions that the British call "Americanisms" are in fact original British expressions that were preserved in the colonies while lost for a time in Britain (for example trash for rubbish, loan as a verb instead of lend, and fall for autumn; another example, frame-up, was re-imported into Britain through Hollywood gangster movies).englishclub.com/english-language-history.htm
And as a teacher of English I would never say that one form of English is better or worse than the other, it all depends on who your target listener or reader is, and you should adapt to the situation.
The majority of my work is proofreading here in Poland, but if I receive a project where the target reader is American I always refer it on to a American proofreader.
This is because I do not know all the slight changes and terminology required, especially if it is a business report where there are a minefield of changes that could be misunderstood.
