The No Dong II missiles Saddam had on order with Kim Jong Il kinda make your "next door" argument moot. When the Spirit of St. Louis hit the ground in Paris, the world shrunk. When Sputnik went up, it shrunk again. When Concorde set records, it shrunk even further.
Learn from the lesson of 9-11. Being able to strike US soil no longer means multi-million dollar missiles and weapons platforms. Neither does this mean we need to now wade into every regional conflict in the world either. North Korea is definately a concern, but for the most part terror groups find fertile soil in the Middle East.
We are currently working on that one and are seeing results.