I am terrified by the prospect of a war with, say, North Korea (not a far-fetched possibility), where China suddenly decides to quit shipping us steel and electronics to fight their allies, and South Korea and Japan, not wanting to get in the middle of two sumo wrestlers, decide the same thing.
Sure, we could re-energize our manufacturing capabilities, but that takes time and money, and how many soldiers would we lose before we are back up to producing all we need.
To me, it's a matter of national security.