NATO is the most powerful alliance in the world. It funds far more than any adversary. I would say—given that the U.S. spends well over $600 billion on defence and has formed the backbone of NATO—it's as good as you can get in the world of human affairs.
The sense of “all for one and one for all” is important. An attack against North America—or an attempted attack, because I don't believe that North Korea has the missiles to be able to reach North America, and certainly not with a nuclear warhead—would result in a huge amount of sympathy and solidarity, but the co-operation of other nations in that domain, far out of NATO's traditional sphere of operations, for me is still an uncertainty. It's such a unique type of issue to be thinking about NATO for North America rather than NATO for Europe.