[Lunatic Fringe]

All North Korea has to do if fit 4 or 5 nukes... they already have missiles that can hit Seattle, San Francisco, Portland, L.A., and San Diego. The Chinese, who now control the Panama Canal, shut down the canal to all US Naval ships... Suddenly, the Far East controls the Pacific.

[thoughtomator]

Except for the slight problem of the massive force the US maintains in the Pacific.