Pretty bloody easy to define the difference between hacking and act of war. Any hacking attack you can simply divert by cutting the connection is not an act of war. A major electro magnetic pulse generated by a thermonuclear war head is an act of war.
For the idiots at the NSA, permanent damage versus repaired disruption. They just need to ask the buddies at the CIA when it comes to their idea of torture, permanent harm equals torture non permanent harm according to them, based upon them being a bunch of sick psychopath sadists, does not equal torture.
So if you ain't using explosives on digital infrastructure it ain't war. No matter how badly behaved the NSA has been, their acts have not quite crossed the bounds of an act of war. Somehow I guess this will be another example of American exceptionalism and when the US does it, it is not an act of war and when any other country does it, it is an act of war and the US must spend another billion dollars on the US military industrial complex per incident or so the lobbyists say.