Between 1935 and 1975, Will and Ariel Durant published a series of volumes that together were known as The Story of Civilization. They basically told human history (mostly Western history) as an accumulation of great ideas and innovations, from the Egyptians, through Athens, Magna Carta, the Age of Faith, the Renaissance and the Declaration of the Rights of Man. The series was phenomenally successful, selling over two million copies.
That series encapsulated the Western civilization narrative that people, at least in Europe and North America, used for most of the past few centuries to explain their place in the world and in time. This narrative was confidently progressive. There were certain great figures, like Socrates, Erasmus, Montesquieu and Rousseau, who helped fitfully propel the nations to higher reaches of the humanistic ideal.
This Western civ narrative came with certain values — about the importance of reasoned discourse, the importance of property rights, the need for a public square that was religiously informed but not theocratically dominated. It set a standard for what great statesmanship looked like. It gave diverse people a sense of shared mission and a common vocabulary, set a framework within which political argument could happen and most important provided a set of common goals.
Starting decades ago, many people, especially in the universities, lost faith in the Western civilization narrative. They stopped teaching it, and the great cultural transmission belt broke. Now many students, if they encounter it, are taught that Western civilization is a history of oppression.