If our manufacturing is eliminated we are going to rely on potential enemies for all of our goods. That makes us vulnerable. Our industial might helped us win both world wars. And it isn't just bombs and planes that we need in crisis. Uniforms, tents, boots, prepared/preserved food, packaging materials, etc., etc.
To Snottie: You shouldn't want your kids in low-level manufacturing jobs (there are/were good jobs too) since you are upper middle class an attended a college that costs over $200k over 4 years. But if you were uneducated and impoverished, you would likely want your kids to find work like manufacturing. The alternative to these jobs is not engineering or nursing, it is illegal drug sales, welfare, poverty, etc. You were born two-thirds of the way up the ladder - that's why you aren't concerned about some of the lower rungs being missing.
The massive pollution from 3rd world manufacturing is another problem. Greedy companies don't just move manufacturing jobs to Asia for cheap labor - the lax environmental regulations increase profits too.