There's enough blame to pass around. Certainly the government did as did the Army Corps from decades of neglect. One aspect that a whole LOT of people don't realize is that the politicians in Mississippi and city and state politicos Louisiana. The way FEMA is set up is that the Federal government cannot go into a state with National Guard troops to assist a state in an emergency or disaster situation (see Posse Comitatus Act)"Who failed New Orleans more in Katrina" Army Corps or FEMA...
Louisiana didn't ask for fed assistance until well after the shit had hit the fan - hence the critical delay.