Of course, there are some differences between British and American English.
A lot of the differences exist between grammar. For example, British English says "in hospital" and "Have you a pen?". However, American English says "in the hospital" and "Do you have a pen?"
Pronunciation is also sometimes different. Americans often hear the r in bird and hurt. British people don't hear the r in these words.
There are also differences in vocabulary between British and American English, for example, "color" and "honour" are written the way the British write them, while Americans write them as For example, "color" and "honour" are written by the British, while Americans write them as "color" and "honour".
The differences in grammar, pronunciation, spelling, and vocabulary are not that important, yet for the most part, British and American English are two similar languages.
It's not easy to write so much in one breath. Be sure to pick me!