To offer some insight on the situation with the world…
For those with the opinion that the US should do something about the situation (that is, militarily), it is advisable to be careful here. You are under the impression that North Korea wants to destroy you. North Korea is on the other hand under the impression that the US is out for world domination.
The posession of nuclear weapons is a right for any country. Much like the right to bear arms. For deterrence. The problems arise from deciding which person is suitable to posess a weapon, just as nobody can own a firearm without going through a check first, so world politics deem to understand this, however it’s much more complicated than a simple background check.
When a person feels threathned by someone else, then owning a gun is prudent. Nobody ever has to use them, but not having one in a difficult situation is unwise. You might as well disband your entire military.
The problem with the weapons situation is, either both sides in opposition give them up, or keep them for deterrence. For example in the case about Syria’s WMD, they apparently agreed to give their WMD up, but only if Israel did the same. If Israel refused, then they would also refuse. It’s a problem of trust.
In such cases, the scales must be balanced. Say for example, the US has a larger military force of manpower. Russia may balance it out by stockpiling more WMD. Any imbalance may make one side more likely to stir conflict and the other more fearful.
Other balances can be made through forming alliances with other countries. We have the EU as an example. The US, Canada and Mexico are joining military under NORTHCOM. Russia, China, India and Brazil are also forming their own union. Depending on the manpower, land and resources of these unioins, one may emerge as the next global superpower. However what this does is create more deterrence for each individual country. For example the US and Israel are allies. Iran and Russia also have similar ties. Any attack on Israel will provoke a response from the US, and any attack on Iran will also force Russia to act. So lest any country preemptively attack one, they risk war with the remainder in the union that the country belongs to.
If the balance is unfavorable, for example with North Korea and the US right now. North Korea may posess nukes and a strong military, but the US has a greater aresenal of nukes and WMD. North Korea also doesn’t have many friends around itself either.
It is unlikely in this case that North Korea will attack the US. All it would achieve would be the deaths of millions of US citizens in a few major cities, this would hardly do anything to a country the size of America from a military standpoint, however a retaliation by the US could utterly destroy their smaller country. To attack the US or even be slightly involved in any other incident against the US would be suicidal. The only deterrence they offer is the threath of a few nukes on US soil, whereby concerned citizens would put pressure on their own government not to provoke them. The strong armed tactic they put up given their situation is a front because they are afraid of the US in the same way US citizens are afraid of their potential to hit any one of them.
As well, it would be extremely risky to begin another war or show of strength at this time given the situation in Iraq. Say the US went to Iran next, while they are occupied there, another uprising could begin in Iraq and possibly Afghanistan and then the US could find itself in an extremely bad situation. War is not a clear cut thing. One domino would topple the other and any escalations would provoke treaties etc and the world would find itself in another world war the likes of which has never been seen, all brought about by nothing but paranoia. With manpower low and too spread out, the use of deadly weapons and nukes would have to be sanctioned. If one fires, then all will fire. Other countries not involved may take advantge of the global chaos to attack one another.
Until there is justifiable cause to go to war, simple accusations of possibly aiding terrorists or harboring weapons that may or may not exist and any pre-emptive strike will simply not do, in could end up being extremely bad.