Chapter 12 in Breisach's Historiography explains the modifications of the traditional historiographic understanding (as the Chapter's title might suggest) throughout from Medieval Europe to the founding of the New World. Breisach also heavily focuses on national identity in explaining some of the changes that occurred over time in historiographic study.
The emergence of nations after the Fall of Rome, what some historians term as the beginning of the Medieval period, caused a sudden necessity and scramble for specific and recorded nation history and identity. The identities founded in respective nations (commonly founded in that of Rome due to the shadow of its expanse) came to create a civilised culture and an ordered society based on an identity for a new nation. In other words, the common mindset of many pre-enlightenment historians was that without a history or national identity, there was no hope for a civilised future. Perhaps this fear derives from the collapse of Rome into barbaric turmoil, but nevertheless, it reigned to be a true fear.
With the introduction of the New World and its people, Europeans were forced to account for entire populations of people with almost no identity with anything close to a "nation". There was absolutely no universality among tribal native Americans in any aspect of life (including religion and politics), all of which was unheard of in the tight parameters of post-Rome Europe. Breisach proposes that the reason behind the Europeans' urgency to colonise (read "civilise") the New World came from a great fear of a foreign and unknown culture. Thus, Europe (especially Spanish conquistadors) saw it their duty to provide or impose a national identity and history on the native populace, through both political presence and religious conversion.
Enlightenment figures and philosophers, which Breisach mentions Francis Bacon as one, began to discuss and challenge the old traditional understanding of national history and identity. For once, it seemed that Enlightenment thinkers were able to establish the ideas of national identity and national history as two different entities of a given nation. This new mindset perhaps destroyed the idea of imperialism as colonies began breaking from their empires. For example, the United States of America created a national identity with very limited history in their breaking from the British Empire.