I recommend you read Benedict Anderson's Imagined Communities! He posits that vernacular languages and the rise of print capitalism and serialisation of newspapers and novels etc. allowed for people to begin to believe they shared things in common with those who they never met and could never meet. How many of your fellow countrymen have you ever met in your life? I tiny amount, yet you believe that as a nation you have similar beliefs goals and lifestyles which make you feel sense of community where none really exists. As far as governments selling themselves, the divine right of kings was the model on which kings claimed legitimacy in European states. This society being envisioned on a vertical axis where the king was at the top with a direct connection to god. This itself was important in legitimising kingship, especially in deeply religious societies. As the French Revolution showed most emphatically, once belief in divine right disappeared, governance based on popular consent became a lot more widespread and popular, and really began to erode the idea that kings maintained their position and the safety of their subjects through a mediation with god.