This is a tough one because no single country fits the bill. Probably the most consistently enduring country would have to be England, who has inserted itself into just about every culture on the planet, from the Romans to the Moors, to North America, to Africa North and South, to India and beyond. But it was Ancient Greece that gave us the first model for a civil society and a government structure to keep order among exploding human populations.
And then we have Italy to thank for the Roman Empire, and then the secular advances in science, art, medicine and commerce during the Renaissance. And where would we be without the adventurous Vikings, the Ancient Egyptians, the Chinese, the Moors, the French on art, food and modern languages,...the list goes on and on.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.