As the title says, really. Was feudalism and its social structures entirely a Norman import? Or was there anything in pre-1066 Anglo-Saxon society that was 'adapted' to Norman feudalism? Was it an introduction? Or an evolution? Thank you!
Questions about feudalism have been answered quite excellently in the past. Feudalism is an abstract, sweeping model that breaks down when applied to the vast majority of specific moments and places in medieval history. Long story short: "feudalism didn't exist", so the Normans couldn't very well have imported it to England. There's also an upcoming AMA with expert panelists covering the topic here at /r/AskHistorians on July 26th.
Note that this doesn't preclude anyone from giving an answer of their own, or discussing the specific socio-economic changes wrought in the aftermath of 1066.
Following on /u/Aethelric , I would ask what 'feudalism' means to you? Because I really don't know what it means when you ask the question. I could answer that England was feudal and Normandy was feudal, and the Anglo-Norman kingdom was feudal, but that would be fruitless, wouldn't it? It wouldn't answer the underlying question of what changed.
This is not being difficult on purpose: feudalism has so many meanings:
That said, the Norman socio-political norms merged with existing norms in England to create variation that was neither wholly one or the other; but it was a duke assuming an existing monarchal kingdom with existing relations. You'll have to get more specific for a fuller answer.