National Myths are important. Nation building is hard. There are many countries today, especially in Africa, which are not nation states at all, but warring tribes locked together within artificial boundaries. They are in fact mini-versions of the European colonial powers which once held sway across the continent. One tribal group seizes power and ruthlessly oppresses and politically marginalises the other tribes.
This is often where national myths come into play. People with very wide ranging interests are convinced there is such a thing as a common or national interest. It's not easy and often involves outrageous historical distortions. British history is a case in point. The Magna Carta was not about protecting ordinary people from arbitrary rule and enforcement of one law for all, but a power grab from a weak king by a powerful clique of very rich and powerful men. Was the Stuart Restoration after the death of Oliver Cromwell really such a good thing? And who were the real beneficiaries of the Glorious Revolution 30 years later which replaced James II with a puppet Dutchman and eventually a German king who spoke no English?
I was reading recently about the British and American generals in North Africa. Many of the Americans seemed to have been raised reading a little history primer called the Red Book, or something like that. In this book the heroes are brave revolutionaries who battle the evil oppressive British for independence and the rights of man in 1776. A lot of supposedly intelligent men took this guff seriously and distrusted their British colleagues intensely as a result of it. The American War of Independence was far more complicated than that – in fact many refer to it as the First American Civil War. Up until the First World War, economic development in the United States was heavily dependent on money from the supposedly despicable British. Of course, building a nation from almost scratch from waves of immigrants is going to involve a very simplistic approach to history and a lot of myth making. But when those myths cost lives, as they did during the Allied campaign in North Africa, it is perhaps time to reconsider them. Americans to this day believe that they live in the finest democracy in the world.  In comparison with most countries in the world, it is indeed a democracy. But it's not a perfect democracy.  The United States is no longer a young country and maybe it's time to ditch some of the national myths and take a mature look at its true history. Trying to impose “democracy” on countries when one's own version may be a little suspect could prove an expensive proposition – both in terms of lives and national treasure.