I tend not to trust the US government at all, but in this case it seems extremely likely that North Korea is in fact behind this as they say. If that's the case, then we are probably seeing a re-orientation of the US government towards a different enemy. Taking tension out of the relations with Cuba, reassessing the torture stupidity and being more proactive about closing Guantanamo have all been long overdue because all these insanities happen only for reasons of interior policy and hurt the US extremely in terms of international diplomacy.
It would make sense for this event to be connected to the recent confrontation with Russia (who might have provided misleading intelligence to North Korea suggesting the US would not react to such retaliation against Sony for embarrassing North Korea's leader), but in any case the realisation they are en route to two extremely costly wars (with no oil to win) -- both of them close to or in China's sphere of interest -- could have prompted some emergency measures by the US government to try and restore international good will.
If I have analysed the situation correctly, we are just seeing the usual manipulations of international public opinion that are a necessary preparation for war in a (pro-forma or real) democracy. For a war against North Korea, not Russia. To this end, the threat must be exaggerated and connected to an American trauma, rather than treated proportionally.