It’s not that hard to understand, but it’s situationally dependent. There are some things which are crucial to an economy. You lose control of them, you lose your economy. OPEC showed an example of this in the 70’s, when they decided, for political reasons, to embargo oil and sent the US economy into a tailspin.
Here’s a recent example: TSMC has a 54% market share of computer chip production, including nearly all of the capability of the most advanced chips. They are located mainly in Taiwan, but have subsidiaries in China and small production facilities in Washington state. (Arizona in process.) In second place: China. Third: Korea. Next, with just 7%: US.
Now recall that nearly every advanced military weapon: planes, smart bombs, laser sights, etc. requires chips — not to mention a significant part of the US economy (remember how “chip shortage” hobbled auto production?)
So even at some cost, it is strategically vital for the US to control its own destiny, and not be subject to the whims of international trade, international politics, or wars we do not control.
Great Britain kept the US a vassal state in the 1700’s by prohibiting the manufacture of finished goods. (After 1790 the US returned the favor, disallowing British imports.) If batteries and EVs are the future, should we not control our own rare earths, necessary for their production, or should we cede that to foreign governments as well?
We watched as the Japanese hollowed out US industries in the 70’s with their own subsidies of steel manufacture and auto production. Good for us - for a while, as we got cheaper prices. Maybe not so good as great swathes of industrial America fell into disrepair and production capabilities were lost.
I will just mention there was a period of 20 years or so where the US had no “heavy lift” capability for putting satellites into orbit; we had to rent space aboard Soviet rockets. Would that be a good idea today, given the current world situation? I can imagine the Soviets closing that door as abruptly as we tried closing their oil spigots, and then where would we be? (Yes, , let’s tell the CIA we have to wait for the Soviets to grant us space for our next spy satellite over Iran or the Ukraine.)
This is a tricky business. Not everything is vital or strategic, and with industry capture I’m sure many (so-called) capitalists will hector the government for funds to re-shore their business - but there are some things which obviously are. We were lucky that rocketry evolved to give us options - but chips (for example) haven’t.
People want their stuff cheap, and complain about the government spending money on these sorts of things - until the spit hits the fan and the precious free market stops working, and then they get delirious.
We’ve used the strategic petroleum reserve many times to smooth the market when bad actors have tried to manipulate it. “Re-shoring” is a different flavor of the same thing: it’s insurance against artificial disruption that lies outside the US boundaries.