North Korea isn't a threat at all to America. They like to put on shows and pretend like they are important on the world stage, but like the short guy who talks big, it's all fluff. The best thing we could do to ruin the North Korean way of life is to give them access to the outside world so the common people can see what they are missing.
No, the United States should not take military action against North Korea. The missile fire did not hurt anyone, so the United States should not respond violently. They should, however, take diplomatic action against North Korea. They should meet with them to discuss peace and a discontinuation of war between the two countries.
If no harm was done to anyone than the best course of action is to keep a close eye on their activity. To say that North Korea did this and that we need to take military action is really pressing the panic button. Yes, the United States should not be sitting ducks either. Best course of action is to tell North Korea that either they stop or there will be action taken against them not just from the US but other countries as well.
Until North Korea makes a move that is a direct threat to the United States we should not get the military involved. At this point they haven't broken any treaties or laws, but we would be if we took military action. We have bigger fish to fry than their despotic leader.