Yes, don't install any languages you'll never use, don't install the printer drivers unless you need them etc. - Btw.: This is also a good tip for those with much bigger harddrives, since every update that includes language files takes much longer if you have multiple languages installed.
All the updates like 10.4.1, 10.4.2 etc will no matter what languages you have installed, install the same update files. So in case you install your system to be only in US English, you will still find the Korean and Finnish and all other languages you didn't install, when you after the update have a look on the programs package contents. So having one language only installed takes initially less time to install, and less space, but it has no effect on any system software update you do after.
(The only exception being the Server edition, which has less languages installed, thus even containing the server software updates, the Server generally takes less space, and the updates are smaller. However, I wouldn't install the Server on that Powerbook G3).
Convert - the programs to remove useless languages are Monolingual and Delocalizer.
I haven't tested those on 10.4 so if anyone tests them, tell if they do or don't work.
Previously, you could run that program once, and after that any software update would still install all the languages you didn't want. So if your system is clearly US English after running that program, if a system update includes updates in e.g. Mail and AddressBook, seeing the contects of those programs > Resources, you could again see all the language resources readded...