I know American English in great detail, including its slang, its clichés, its style and usage. With British English I am less richly familiar, but I have a good sense of it. And I have had at least some exposure to Indian English. But what about Australian English? New Zealand, South African, Jamaican English?
I have found my exposure to other Englishes — including the broken Englishes of non-native speakers — to be rewarding. I should make an effort to pursue the literatures of other Englishes.