Living in Southern England, I understand English spoken properly and have no difficulty with the American accent.
We speak English properly. We just perfected the language by pronouncing words the way they're spelled. You know, we say 'r' at the end of words that end in 'r' instead of saying 'ah'. We also fixed the spelling of many words like center, theater, shop, favorite, etc to make them agree with their pronunciation..
Stuff like that.