I think playing as Tannu Tuva is the hardest in the game.
Played as Argentina and it went really good.When I marched into Uruguay,Allies declared war on me and for a short time captured Buenos Aires,but after annexing Uruguay,they agreed to peace.When I invaded Paraguay,the same thing happened,but somehow I was able to capture the British Home Fleet sent to Rio de la Plata,2 Carriers,several battleships...At this point I had more BBs than the Brits!Luckily for me the war in Europe soon broke out,and I immediately joined the Allies.
After it I worked up north,Chile,Peru,Bolivia,Ecuador,Colombia all fell into my hands.Then turned to C.America and conquered all the nations there for Britain+Cuba for me.
War in Europe+Africa was not going well for us,with Greece,Portugal and Yugoslavia on the Axis side and Britain German-occupied.In Africa the Portuguese even annexed South Africa and all of Egypt and Near East fell to the Italians.
But then Soviets began marching,at first it was a stalemate,but in 1943 they advanced quickly and in 1945 all the continent except for Romania,Spain,Portugal,Switzerland,Scandinavia and-good for them-the Baltics was Soviet,plus 1/3 of Africa.When the Axis defences broke down,I turned to Europe,and took Rhodos,Dodekanes,Crete,Sardinia;in Africa big parts of Namibia,S.Africa,Angola,Mozambique.I think you can really call this Greater Argentina.
I think my next step will be transporting troops to the West Pacific to take some lands from Japanese and Siamese,who have taken everything from Pakistan to Tokyo and Kuriles to New Guinea.