To take an example from an industry I know well, we (meaning the IT industry) used to employ THOUSANDS of people to manually string together something called "magnetic core memory" (they looked like a fabric of tiny metal donuts string together in a weaved pattern).

Today memory is made completely by machine. We make plenty of it - to say nothing of all the other kinds of chips we make - almost completely automated - done by robots.

I've seen the same thing happen in sector after sector. You don't need as many people to build a Ford as you used to. Not by a long shot. But now you're building a $30K-$40K Ford with those fewer people instead of the 42K-$3K 40 years ago (the price of the car outstripping inflation for a variety of reasons)

Bulding up the manufacturing sector will be good for things like our trade deficit but it's not the panacea for employment as it just doesn't take as many people to build stuff as it used to.