Legend has it that when the Harry Potter books were published in the United States, all of the Britishisms were removed with a few exceptions that were deemed essential to the books’ identity, such as ginger, used to describe Ron Weasley’s hair. I wonder the extent to which such translation is generally undertaken. I would imagine it’s routinely done in matters of spelling, as programme, centre, and such would be jarring to American eyes, whereas vocabulary, especially in dialogue, could justly be seen as part of a novel’s
The actual title of a book would appear to be a special case. A British novel called Ten Things I’ve Learnt About Love, by Sarah Butler, has just been published in the U.S., and the fourth in the title word is still spelled Learnt, rather than Learned. That made me curious about the history of the two spellings in the two nations, and so I did a Google Ngrams search for the phrases has learned and has learnt, the results of which are below.
The chart shows that learned has always been the preferred word in both places, though around 1920, learnt (red line) was briefly as popular as learned (yellow line) in Britain. U.S. learned (blue line) as always kicked the butt of learnt (green line), and unless Ten Things I’ve Learnt About Love has Harry Potter-level success, it is likely to continue to do so.