1939
1 star: Mongolia(far from Europe, facing strong generals).
2 stars: Australia(you've said that)
1943
1 star: Hungary(no space to develop)
2 stars : Romania(facing the stong Soviets)
1950
1 star : South Korea(always dies fast)
2 stars: Japan(the great People's Republic of China will nuke it!)
1960
1 star: South Korea(do I need to explain one more time?)
2 stars: Germany(the biggest conflict burst out here)
1975
1 star: India(that teeny city is too weak)
2 stars: Brazil(way too far, facing the BrisbaneII,Bogota)
There will never be a difficult 3 stars country, never.