No post from me about excellent copywriting would be complete without mentioning the folks at Velocity Partners. A B2B marketing agency out of the U.K., we've featured co-founder Doug Kessler's SlideShares (like this one on why marketers need to rise above the deluge of "crappy" content) time and again on this blog because he's the master of word economy.
I think each tries to accommodate for a worldwide audience. In general, as a copywriter, you need to be prepared to write for different audiences (and a worldwide audience), especially in this digital age. And the underlying principles of copywriting will be the same, wherever you learn them – but when you come to crafting the copy itself, you’ll just have to be aware of UK/US spelling and phrasing. Good question, Evan