Applecare does offer at least some international support. I bought a powerbook in New York before I left to live in London (last September). The computer and applecare agreement are both registered to a US address. There had been a problem with the magnetic clasp on purchase but since I was heading right out of town, the guy at the applestore suggested I just deal with it in London.
I didn't bother until more recently when there was a problem with the connector to the power adapter that needed to be taken care of. I took the machine to the store on Regent Street and they sent it right out to an apple repair center here (in Dublin I think). It took a slight bit longer than these things take in the states, as everything here does, but I got it back practically brand spanking new. They replaced the bottom half of the case and did a few other repairs I hadn't requested. Overall I had a better experience than I have had in the US with previous powerbooks. I also made use of telephone support once and there was no problem to just connect me to a support guy here (also in Dublin).
If you are travelling to a city like London, Tokyo or Sydney, let's say, you will have no problem. That being said, I doubt that you would have an easy time trying to get your powerbook repaired from a place with less reliable shipping carriers and transit routes. I wouldn't bother from any place where say, fresh drinking water would be more valuable and rightly of greater concern than your powerbook (ie most of the world).
