I think Ward-Perkins made an excellent case that it was the Vandal occupation of Africa that brought down the West. Italy itself was simply not able to support the administration of the provinces. Seemed to do fine as long as North Africa remained a taxable province without disruption from migrating Germans. The barbarians had to be managed; settled here and there, accommodated in various ways, but Ravenna could still perform as an administrative center. Once Africa was gone, things went down hill pretty quickly.

Well, it needs first to be remembered that entirety of Rome as a political entity did not fall in 476 A.D. Only the Western half of the Empire ceased to function. In the East, the Roman state continued to exist and thrive for another thousand years, finally succumbing to the Ottomans in 1453 when they captured Constantinople. Although we often refer to the Medieval Roman Empire as the Byzantine Empire (a convenient delineation that allows for distinctions to be made between it and the Empire of Late Antiquity or earlier), Byzantines continued to identify as Romans, viewed their state as the Roman Empire, and knew their emperors continued an imperial tradition directly traceable back to Augustus. Any grand narratives about the "decline and fall" of Rome are thus complicated by the survival of the East, and the nature of "decline" is heavily debated by scholars.