[quote=The Nexerus]
Is there a list of nations that have been reserved in advance?
[/quote]
Prussia, Armenia, China, Spain, Ethiopia, Britain, Georgia, Persia and Liberia. 

Other countries that have a set canon but aren't being played include Japan, USSA, Canada, Brazil(I think), Russian Republic, the Finlands, Slavic Union, most of East Asia and the Ottoman Empire.