Oddly enough if you were to check out other Apple websites, such as Apple Singapore, you will realize that the Siri feature is not listed, and not surprisingly so especially since those features demonstrated (such as local searches and restaurant bookings) during the announcement was made for the US market only.
However fret not, with Siri being one of the key features exclusive to the iPhone 4S, Apple has not forgotten about their international customers, and according to the Siri FAQ, international users can expect local maps and local search support to start arriving some time in 2012.