This does the trick. It needs to be put to the scripting tab for it to have effect on tags, as opposed to the file naming tab.
$if($eq(%releasecountry%,XE),$set(releasecountry,Europe),)
I think I made some poor word choices in my original reply.
Actually all of MB’s country codes follow that standard. MB’s decision to do a “perfect implementation” of the standard is the big reason why we have XE instead of “Europe”. That decision has at least one positive I can think of: it makes translations more elegant. One negative thing is that XE = Europe only for MB and if the data is used somewhere else they need to know what MB means by XE.
Also since EU countries are a subset of European countries (at least currently), it’s not wrong to list an “EU release” as a European release, just less accurate. Omitting EU could even have been an intentional choice on MB’s part.