As a Scotsman, I put up with being told by English people that I should speak more proper English.
I see the Americanisation of the English langauge as nothing to fret about, it's a dialect, bound to happen anywhere, especially with the amount of different people that made up America. Even in it's early years you had English, Scottish, Irish, German, Italian and so on, bound to effect any language.
Plus, I've been to some places in England where the English is worse than it is in America, see - Newcastle.
Oh, and we've butchered it to a point as well, so David Mitchell can take his wee poncy English middle-class etonian rants and shove them up his own arse because not everyone talks like they walked out of a period drama. Prick.