A translator colleague says he may have to ‘avoid the Brits to be a good translator…’ I thought that was hilarious. I believe it’s harder for the typical American because of the almost monolingual (safe for some Spanish) situation of the country. For linguists or people who grow up in multi-lingual contexts, code-switching is a near natural phenomenon. British and American English vary but for the most part, it’s the same core language.  And I’d dare say that in terms of authenticity, the former carries more weight. Same applies to say Canadian vs French French or Belgian vs French French. That’s where a localization expert or a translator with sufficient cultural knowledge comes in handy!