There's a bunch of speculation going on in this thread based on personal anecdote... let's have a look at some data shall we?
Let's compare the ngrams of the words 'bespoke' 'customized' and 'customised' between the USA and UK:
You can see that in both cases bespoke had its primetime in the first half of the nineteenth century, falling off and hitting its nadir at around 1980, with a resurgence in usage since then.
However, it's also clear that the usage of 'bespoke' is more common in British English than it is in American English, although not by a huge margin - current usage (in books) is about 70% more common in British English than it is in American English.
Obviously the huge cavéat here is that these ngrams describe how language is written in books, rather than how it is spoken.