Final answer:
Egypt's strong, centralized state and resistance to invasion can be attributed to its geographic isolation, early unification under a single government, and established bureaucratic and military systems.
Step-by-step explanation:
The best explanation for why Egypt, unlike Mesopotamia, created a strong, central state that resisted invasion lies in geography, early unification, and cultural identity. The unification of Egypt around 3150 BCE during the Early Dynastic Period led to the establishment of a bureaucratic system and the centralization of political power, signified by the institution of the pharaoh and distinctive religious practices. Unlike the city-states of Mesopotamia, which were often in conflict and subject to invasion, Egypt was geographically insulated by deserts on both sides of the Nile Valley and by the Mediterranean Sea, where sailing technology was not advanced enough to facilitate large-scale invasions. These natural barriers, along with Egypt's strong military and bureaucracy, contributed to the creation of a stable and centralized state that could resist invasions better than its neighbor, Mesopotamia.