At the same time, the US is one of the biggest markets around, so it provides a reasonable case study and it tends to be the first to get any upgrade. It would be a nightmare to try to do the same for Europe for example because of the fragmentation.
is the US really the first to get an upgrade? Most of Samsungs phones are launched first elsewhere, and US versions later come with their own carrier specific versions. The plain Galaxy S is not on that chart, and it would have received the upgrade before all the US variants.