Typically yes, but I don't know that you could definitively say "always" since there is of course potential that some devices I'm unaware of don't follow that pattern. Usually, though, there are different firmwares due to regional differences in carrier bands/settings, wifi channels, and other considerations (localization, possibly).
As an example, though, take a look at the stock firmware listings for the Motorola Xoom. There are a whole bunch of different images available, divided up by both model number and region.
There's also a thread here where people discuss how you could try to go about flashing a firmware from a different region via Odin without affecting your connectivity. I don't know much about the process myself, though, as I've never done this.