Answer:
The process that saw Western Europe going from a unified Roman Empire to independent nation-states was: Roman empire weakens and barbarians take hold of Roman lands. Barbarians establish numerous Kingdoms and nation-states. Monarchs share power with nobles in the feudalistic system.
Step-by-step explanation:
The Western Roman Empire comprised the western provinces of the Roman Empire at any time during which they were administered by a separate independent Imperial court; in particular, this term is used in historiography to describe the period from 286 to 476, where there were separate coequal courts dividing the governance of the empire in the Western and the Eastern provinces, with a distinct imperial succession in the separate courts. The terms Western Roman Empire and Eastern Roman Empire were coined in modern times to describe political entities that were de facto independent; contemporary Romans did not consider the Empire to have been split into two empires but viewed it as a single polity governed by two imperial courts as an administrative expediency. The Western Roman Empire collapsed in 476, and the Western imperial court in Ravenna was formally dissolved by Justinian in 554. The Eastern imperial court survived until 1453.