Virtually all our electronics are made somewhere else. We can't even build our own infrastructure[0]. Who will build the Liberty Ships[1]?
[0]http://www.nytimes.com/2011/06/26/business/global/26bridge.h...
But if we stop building - even for a few years - we will lose all that and be back at square 1. This is why the Navy has a huge number of aircraft carriers. We don't need that many really, but if we stopped producing them we would lose all the institutional knowledge and experience. So they dribble one out every 5 or 6 years so that lots of people are constantly working on it.
That will not happen again. It is a bygone era. Now it will either be country to country attacks (Iraq, Afghanistan, Vietnam) or full blown nuclear wipe-out. In either case protecting Cleveland won't make much of a difference.
Decimation? Of the labor force, maybe. The U.S. is still the largest manufacturer in the world:
http://blog.american.com/2011/01/the-demise-of-america%E2%80...
We manufactured more in 2009 than Germany, Japan, Italy and the U.K. combined. China's growing fast, but we're still outputting something like 40% more.