For some reason (crap translations ?, just prefer using English ?), it’s common for some non-english speakers to run their desktop with an en_US locale but then to have difficulties that stuff like openoffice.org, etc. defaults to letter size paper and inches for display units. So my modest suggestion is that if you want to use an English locale then a non en_US locale like e.g. en_GB will default to the way more common A4 paper format and also default to cm for units. Even better for most europeans, using en_IE will also give you A4, cm and additionally the default currency as Euro.