I'm making a 1984 mod for myself and a few friends. I also have another mod but I'm using the easier of the two first
So it's divided into:
Region Code:(2689)Oceania: All of North & South America (Greenland), All of Oceania region, Papua New Guinea, Iceland, United Kingdom, and Ireland.
Region Code:(880)Eurasia: Ussr, All of Europe excluding: Iceland, United Kingdom, and Ireland, Mongolia, and Turkey.
Region Code(1984):Eastasia: China, Japan, Pakistan, Nepal, North and South Korea, Afghanistan, and Iran.
They are at war throughout their history, but do not attack one another directly so the solution is to divide the remaining areas into three warring colonies with well protected capitals (African Oceania territory would be their colony).

I also tried what you suggested but I have no idea how to recache and I've tried looking everywhere on the forums.
I did however manage to have Oceania pop up in the selection box for the sandbox. However the game didn't start nor
did any of the countries outside of North America listed under Oceania disappear from selection such as Australia. If it helps I'll upload
the very early alpha files (They only contain a very basic Oceania). Other than that your advice saved me a fair deal of time.