Something I don't hear much of is the fact that we won WWII because of our manufacturing capabilities. Plain and simple.
We were able to quickly turn button factories into bullet factories.
Even relying on our current manufacturing ability (which is STILL pretty impressive) Any automated machine equipment used in this country will eventually need parts from overseas to keep it running. We'd be ok for a little while...
... but that's about it.
I think you'd be hard pressed to find someobody under 40 years old that even knows what a lathe is, let alone how to use one without a computer attached to it, and a guy who flies in from japan to fix it every time it breaks down.
One might also wonder where we'd get raw materials like steel should our connections ever get broken with the rest of the world.
Yeah - we're becoming a service nation...
Service nations do what they're best at, serve the rest of the world.