British vs. American English
In my view, a largely overestimated issue. Spell ‘center’, ‘honor’ and ‘realize’ and everyone will take it for American.
At the risk of pissing off those of my readers who differ, I think that the deviations between British and American English are greatly overestimated.
In fact I have found the most fiercely dogmatic advocates for which variant ought to be preferred in Germans who have lived in the U.K. or U.S., respectively. In my experience, though, few English speakers from outside either country are susceptible to note the differences unless actively looking for them (I usually don’t, and I read a lot of English literature). With the number of non-native English speakers worldwide exceeding that of native speakers by factor three, globalisation makes its own contribution to glossing over the divergences.
Although the Wikipedia article on the subject alone comprises 40 A4 pages, the actual differences are most obvious in pronunciation and thus irrelevant for what I do. Then there are of course minor grammatical and lexical preferences – the latter often to do with the more private aspects of life (as in toilet vs. restroom). Hardly any cause mutual incomprehensibility.
For most practical purposes of marketing communications, therefore, four simple rules usually perfectly suffice to optimize a piece text for American English: locate things in the center of a theater, honor the particular flavor of someone’s humor and realize that Americans prefer sedans and station wagons over saloons and estate cars. The respective spell-check in MS Word will do the rest.