why e US will not invade North Korea
the United State of America will not attack North Korea because there's no incentive to do it. firstly, NK does not have any nature resources unlike Iraq which has oil. secondly, NK actually has the capability to attack US and Japan, it's close ally with inter-contenential missiles in the event of an attack. thirdly, NK is China's neighbour and China would not like to have US in it's backyard and the fact that China is able to attack US with its missile, or take advantage of the situation to invade Taiwan doesn't really help either.
*side-issues* the US is developing/building a missile defense shield. and what does that symbolise? basically, if the programme works, it will defend the USA and it's allies from a missile attack, but from what i know, it's still in its development stage and it will not be tested/working/fully operational in the near future. but even if the program doesn't work, it still has certain effects. it's telling its potential attacker that it's developing a missile defense shield and has the ability to develop a missile defense shield. therefore, a first-strike missile attack on US now or in the future might not succeed and the US will counter-luanch its missiles unto you... blar blar blar. it's a mind game. e.g. during the taiwan straits crisis, sending a carrier group to the taiwan straits doesn't mean that US wants war with china. it's more likely that the US is telling China that it's commited to defending taiwan and is serious bout it. so there you have it. my 5 cents worth of analysis. (back to work, lunch's over)