There is no federal expertise in capping oil blowouts. There is no federal agency tasked with repairing oil spills. There is no expectation that the federal government should be able to respond instantly to a disaster like this. There never has been. For better or worse, it's simply not something that's ever been considered the responsibility of the federal government.
Since 1968 there has been a National Oil and Hazardous Substance Pollution Contingency Plan. For some reason the government doesn't have the expertise in deep sea well capping but dealing with oil spills has certainly been "considered the responsibility of the federal government."
Why we were unprepared for this particular disaster is an issue for future investigations but theoretically we should have had some plan in place.
I came upon this early in the week when I was researching an idea I had about creating a Superfund type program for oil drilling disasters. Lo and behold we actually have contemplated a disaster like this before!