Our old friend Sackerson and I have periodically debated between ourselves what attitude one should take as regards national self-sufficiency. On the one hand, to be dependent upon imports for any vital need is to offer a hostage to fortune in difficult times. The very concept of the nation-state is often identified with this situation. Only when man (or proto-man) existed in isolated and self-sufficient communities could reliance on trade be thought of as irrelevant. On this analysis, nation-states exist when, and because of, the move to specialisation and trading, which requires the thus-extended and non-independent communities to organise in such a way as to (attempt to) make this a viable state of affairs. Sometimes, typically in warfare or conditions of famine etc, such arrangements fail. History is littered with case studies, Germany in WW2 being a fine example: suppose the Third Reich had been self-sufficient in raw materials ..? Today, China is endlessly nervous about its own dependencies on imported raw materials - just as we are about their monopoly on rare earths.
On the other hand: given this potentially fatal outcome, why do people surrender their self-sufficiency in favour of specialise+trade at all? Because it is a thousandfold more efficient to do so - in "normal" times! Even George Monbiot rapidly tired of life as a subsistence farmer; and many on the green-left reject what is termed "deep adaptation" (= living in caves). All capitalist instincts (and not just doctrinaire capitalism either) speak in favour of doing what we're good at, and buying those wonderful things someone else excels at.
So - how is the balance to be struck? How does a government decide what percentage of, say, the country's electricity should be generated within its own borders, or (a similar problem) how many rarely-to-be-used snowploughs should litter one corner of Heathrow airport? How much Risk Capital should a bank hold? How high should the Dutch dykes be? Or how big should be our armed forces, to rectify matters when "normal" affairs get out of hand? In the abstract: how much of our resources should be tied up, how much potential comfort should we forgo today, against adverse future contingencies?
Let's cut to the chase: we are on a continuum and there is no definitive socio-economic calculation to be done. There is indeed a ton of maths and modelling we can do, with Nobel prizes on offer for advances in technical Risk Management analysis - but the basic inputs include critical and wholly subjective judgements**. So nobody should get hung up over what can be portrayed as, or mistaken for, a science. Only towards the very ends of the spectrum can anything strong be stated, e.g. (a) the Vatican isn't a viable state, and needs to be embedded in something a lot bigger; (b) Canada is very fortunately placed, and very unusually so (and even Canada is somewhat parasitic on the USA for defence); and (c) the dykes had better be higher than the average high-water mark.
Covid-19 makes this otherwise rather academic debate ultra-real; climate change ditto. (For example: we may note that in some quarters it seems to count as wicked not to be self-sufficient in ventilators and virus testing chemicals; but just fine to depend on migrants to staff the NHS ...) And when it comes to reordering the world in due course, some highly motivated parties will be competing for control over those "critical and wholly subjective judgements".
We can at least be grateful they won't include Bernie Sanders^^ or John McDonnell.
** Another post, maybe. I can bore for England on this
^^ Definitely another post! There are fascinating developments on the lefty front