Until now, the warranty applied on Airport station and Apple TV was tied to the regulation applied in the country where the unit was purchased (unlike computer). This is not true anymore, as both products now feature an international warranty and after sale support. So, you will be able to make it repaired in another country. For Airport Station you will have to keep in mind that the channels dedicated to wireless network are different depending on countries, so, the repaired unit might have different settings:
USA and Canada: Channel 1 to 11 for 2.4 GHz. Channel 36-48 and 149-165 for 5 GHz.
Japan: Channel 1 to 13 for 2.4 GHz. Channel 36-64 and 100-140 for 5 GHz.
Europe: Channel 1 to 13 for 2.4 GHz. Channel 100-112 and 132-140 for 5 GHz.
Australia, New Zealand and Hong-Kong: Channel 1 to 13 for 2.4 GHz. Channel 36-64 and 149-165 f
