Siobhain Butterworth, reader's editor of the Guardian, is discussing the occurrence of Americanisms in the paper. It seems that they receive complaints about this. In itself, it isn't a subject of interest to me. American English, British English, who cares? So long as people make themselves understood, well and good; and if they can speak and write in an interesting or arresting way, better still. Any words available for these purposes may be called upon.
I do, however, want to support the correspondent who wrote in to grumble that '"ass" was used instead of "arse"'. This is not because 'ass' is an Americanism, but just because it's an inferior usage, or so it has always struck me. 'Arse' is plain and upfront, so to speak, unashamed of any coarseness listeners may find in the word. 'Ass', to my ear, is coy and, though not exactly a euphemism, carrying something of the same intent, trying to smooth away some of the roughness. This effect comes partly just from the loss of the 'r' and consequent shortening of the length of the vowel, but partly also from the shared meaning with the animal - as if the speaker or writer might be hoping you'll be deceived by the ambiguity. 'Arse' sounds more blunt and honest. With 'ass' a politeness is intruding in the wrong place.
Of course, it's a word you may not wish to use, and one that most of us won't use in at least some contexts. But when it is used, its 'straightforwardness' is part of its point. Use it or don't. But respect its integrity.