There is a misconception - indeed the very reason you're trying to nail it down--that the levee broke Monday during the storm. It was much later, likely sometime overnight Monday.
In affect, New Orleans real problems didn't begin until Tuesday. The stutter-step certainly slowed FEMA's march to NO, since they didn't know how desperate NO would become until 24 hours after the storm hit.
Heck you had people on Bourbon Street on Monday celebrating because they thought New Orleans had dodged the bullet.
You do realize that FEMA had to manage rescue efforts over an area the size of Great Britain don't you? Why is it the rescue effort are going marvelously every where BUT New Orleans? Couldn't have anything to do with the LOCAL Govt being responsible for the 1st Responders? Couldn't be that the locals FAILED to provide the FEMA teams ADEQUATE PHYSICAL security now could it? Just what did all those Dept of Homeland Security $$$ given to the City of New Orleans since 9-11 BUY me? Can you imagine what would of happened if instead of a slowly developing Hurricane that most people fled from in advance, Al Qeda had blown up one of the levees with a fertilizer bomb on a normal business day?