What did Adam do wrong in blaming Chavah?
Rashi 1 : Hashem did Adam a favor by giving him Chavah as a helpmate. Blaming Chavah for his sin was the ultimate act of ingratitude.
Seforno #1: Worse still, he had the Chutzpah to place the blame on Hashem for giving him Chavah.
Seforno #3: When a sinner is confronted by his sin, the correct thing to do is to confess to having sinned and to do Teshuvah (like David ha'Melech, when rebuked by Nasan ha'Navi), and not to blame someone else.
The Ramban also cites this explanation, in the name of Chazal.
Why did Adam eat when Chavah gave to him?
Moshav Zekenim : She hit him until he ate. Before he ate from it, he did not have knowledge to protest. 1
If so, why was he punished? Perhaps it is because the sin came through his adding to Hashem's word. I.e. he made Chavah think that Hashem commanded not to touch the tree. (PF)
Hashem asked Adam why he ate. What was the answer "the Ishah gave to me"?
Ramban: What Adam meant was that, since Hashem gave him Chavah as a helpmate, he believed that, whatever she advises him must be the correct thing to do 1 .
Chachmah u'Musar (2 p.278): Full regret must uproot against the source of sin. Women know to entice their husbands. I need to uproot the ability to be enticed.
To which Hashem replied that it was obvious that he was not permitted to follow her advice against Hashem's express command.
רש"י: כאן כפר בטובה: כיצד רואים שהוא כפר בטובה?
גור אריה: הוא לא אמר 'אשתי נתנה לי' [אלא תלה בקב"ה- אשר נתת עמדי].