The statement that best analyzes the impact of Charlemagne’s changes on social structures within feudal monarchies is:
Nobles became an increasingly powerful social class due to land being divided among lords by monarchs.
This reflects the reality of the feudal system, where land ownership was a key aspect of power and influence, and Charlemagne's policies often involved the distribution of land to nobles in exchange for loyalty and military service. This helped to solidify the role of nobles within the feudal hierarchy.