What happens if Marine One's rotor blades fail?
No helicopter can fly if the blades fail.  The overwhelming majority of the lift produced, required to counter gravity, is from the blades. There is some lift from lots of other parts of the helicopter but all combined, nowhere near enough to keep it flying.  The blades are also required to manoeuvre the helicopter. 

It is also most probable, and this what usually happens, that if one blade fails, or is lost, the resulting imbalance in the heavy, fast rotating rotor assembly leads to instant breakup of the aircraft.

The wing at the rear is called an horizontal stabiliser and its job is to push the tail up or down, depending on the load and speed of the helicopter, to keep the fuselage more or less level throughout the operating range of the craft.

Marine One would simply plummet if the blades failed.