If Americans speak English, why must they have an American dictionary?

While we speak English, many words are spelled differently in America, and there's also slang words - which requires our own edition, the "American" Dictionary for the English language.

Americans have been pushing for a language of their own for quite some time now.Here in the UK, we use words that are spelt differently. Example colour-color. When I use 'spelt and colour', Google underlines them, but these are proper words in the Oxford English dictionary.

In time our language will change dramatically.

english and languages,,all of them,are as varied in species genus and subgroups as cat 

 & dog fur color,accents quirks native expressions same with birdie chirps,,dictionaries are usually incomplete because of rapid changes even as they first are reissued and go to press

What kind of dictionary do you think Americans should have? A French dictionary? A Spanish dictionary?  We speak English--which is a general term. We speak AMERICAN ENGLISH which requires a dictionary in AMERICAN ENGLISH. Why isn't that clear?

Because ..

1) There are certain spelling differences:

Americans leave out the u in certain words

Flavour ... Flavor

Colour .... Color

Americans use a z instead of an s in certain words

Fertilise .. Fertilize

Socialise .. Socialize

2) There are times when a completely different word is used:

Pavement .. Sidewalk

Courgette .. Zucchini

Aubergine .. Eggplant

Hint: the first dictionary was not invented by someone trying to understand English.

let alone speak,

they don't even understand english.

"are you through" say that to an american.

Because English has beome the lingua franca for world commerce; word meanings in various countries have evolved differently than in America. Examples: the American English word "elevator" has been replaced by the British word "lift" and the British word "football" has been replaced by the American word "soccer".

The first settlers spoke English.  The languages have diverged over time as they always do.  At some point a language is considered sufficiently different that it gets its own name.  In the meantime, the form of English spoken in the US is technically American English pidgin just as the form of English spoken in Nigeria is Nigerian English pidgin.  For some odd reason the US claim to speak American English.  We hope they soon start calling it American.  Then they could leave our language alone.

Because, despite our similarities, the United States and England are separated by a common language. 

Do you mean United Statesians? They're not the only Americans. All inhabitants of the Americas are Americans. United Statesians havs arrogantly appropriated the term for themselves.