Ok realnames if I'm Wrong (as you so boldy proclaim, while I simply disagreed), do a search in google for "sublease new york apartments" and tell me what google suggests ("did you mean" )?
next do a search for "sublet new york apartments" and tell me if google suggests anything...
How about web pages:
Google results: Sublease New York Apartments: 1,440
Google results: Sublet New York Apartments: 15,600
It seems to me that sublet is about 10 times more common.
Of course I'm sure those are all U.K. pages dedicated to renting New York apartments, because as you definitively state "its a word rarely used except in the U.K."...