The building of the transcontinental railroads fuelled the popular idea of

Manifest Destiny

Explanation:

The doctrine of Manifest Destiny is a phrase and idea that expresses the belief that the United States of America is a nation destined to expand from the Atlantic coasts to the Pacific. This idea is also used by supporters to justify other territorial acquisitions. The supporters of this ideology believe that the expansion is not only good, but also obvious (manifest) and accurate. This ideology could be summarized in the phrase: "By the Divine or God's Authority". The phrase happened to become a doctrine over time.

i think it was because of how protected egyptian civilization was was which allowed them to evolve without much outside influence.