Most NATO countries have limited, if any interests in the Asia-Pacific region, and a conflict there would not necessarily involve them whatsoever. Most NATO countries have essentially no ability to project power in the region. It's also not the purpose of NATO.
The US's allies on this issue are South Korea, Australia, the Philippines, and Japan. Japan has one of the most powerful armed forces in the world by most measures. They constrain themselves with policy and weapon choices, but a warship is a warship, a jet fighter is a jet fighter, and Japans are very, very good.
Unlike Saddam in 2003, North Korea has actually detonated nuclear devices 5 (6?) times, and is actively testing increasingly capable ballistic missiles. The threat from them is not theoretical. It's real. And while they don't yet have a submarine launched ballistic missile yet, marrying the two technologies is not beyond their capabilities. Every other hurdle they've had ahead of them they've managed to surpass. Given enough time, they'll surpass this one too.
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That's slowly changing. And the US is encouraging that change.