You're essentially arguing that the US is paralyzed due to the possibility of unknown unknowns. It might make sense to think that way to write a book, or for brainstorming large-scale disaster planning. But every system has someone responsible for it, and that someone needs to be responsible for securing it to best practices.
From a policy perspective, we wouldn't just accept that a power plant's energy handlers hum along unsupervised and so could fail catastrophically due to some latent problems. Rather, there are inspection and maintenance schedules to do the diligence of adhering to best practices. That same diligence needs to be brought to bear on a plant's information systems, and if those information systems are hooked up to a WAN (for which there may not be a choice), then that diligence needs to be applied to handling abstract adversarial attackers.
Not doing that is a grave failure, and what seems to be going on here is a "nobody's fault" because it's not in the plant administrators' or vendors' interest to look down and see that they're already past the edge of the cliff. But allowing it to persist is simply kicking the can down the road in an unsustainable manner.
Best practices have been and continue to be the lowest common denominator and an abysmal failure. Compliance solves nothing, and it is a make work project for compromised jobsworth consultants who lack the standing to tell anyone they told us so.
What I am arguing is tech and poor management culture in energy and infrastructure companies is the weak link that gave away the empire.
I basically agree with everything you've written here, but saying it already "gave away" basically means giving up. Whereas this "cyberwar" meme is a call to action, and so I think it bears repeating that on the technical side the problems are extremely straightforward. Rather the real problems are organizational/institutional, and that's where blame needs to be directed - so that the call to action doesn't lead to further obtuse top-down measures like more procedure-bound certification-based consultants or a national firewall.
Worthwhile top-down things that could be done would be say a national bug bounty on any critical infrastructure (and indemnification for any incidental damaged "caused" by researchers, rightfully assigning it to plant operators instead), or perhaps even a wholesale repeal of the CFAA to stop papering over the fundamental nature of the Internet being hostile noise. Stop discouraging 12 year olds from playing around with infrastructure for the lulz, and make administrators have to deal with reality rather than continuing to ignore it.
A.K.A. a time of war, like the ones that rocked Europe and the rest of the world through the 19th and early 20th century, as regional powers struggle to become the new global hegemony.
Those who desire an end to the Pax Americana, be careful what you wish for.
People are irrational. For the sake of transgressing a minor boundary, wars have occurred, even if the boundary has no strategic value. Suppose there are patrols into barren hinterland, that could still cause a war, even though the lands could not support permanent habitation.
It is theorized that Germany started WWI because of growing popular support for the socialist party.
First, calling these issues "homeland defensive postures" makes no sense.
I don't understand how you can view the current situation as "regional powers asserting themselves." NATO now borders Russia and the US effectively controls two states bordering Iran. The only bold moves any of those states has made was Russia's move into Crimea, but even that was Russia preventing their port from switching over to NATO.
I've argued before that U.S. critical infrastructure vulnerability will prevent it from intervening in Taiwan and Hong Kong. Its lack of a strong homeland defensive posture on infrastructure has emboldened regional powers like China, Russia, and Iran to assert themselves over local NATO allies without fear of US retaliation. e.g. The US isn't going to risk a dam flooding or a long term grid failure over a distant minor ally. Arguably, NATO made sense when partners could defend their infrastructure, but the mutual aid commitment becomes a suicide pact when your cities can be turned into tribal warzones by depriving them of power, payments, and fuel. Nobody wants to get drawn into that by a minor ally.
That's the weakness that creates the power vacuum into which warring parties pile in. We do indeed live in interesting times.