Really? Let's say the US found itself cut off by military blockade from the rest of the world, like in WW2. No optical glass from Germany, Japan, Russia or China. Where is the optical glass for all the binoculars, submarine periscopes, drone cameras, spyplanes, spy satellites, rifle scopes, laser range finders, night vision goggles, jet fighter HUDs, smart ordinance, and all other things optical the defence is going to need, going to come from?
Anecdote from my dad, who worked at B&L before, during, and after WWII. Before declaring war, FDR put the USA on war production "Arsenal of Democracy". A Merchant Marine ship loaded with optics got sunk on the way over... a significant strategic loss. Thereafter, optical supplies were split up among several shipments, tagging along with other stuff. Optics were pretty high up on the important list. The per pound cost ($, effort, time) were very high... not to be loaded onto one ship anymore. Existential? Maybe not as much as a pair of A-Bombs, but still significant.
Lately, the word ~existential~ has been so watered-down, overused and hackneyed by politicians... that we might want to give it a rest for a few decades. A mask, nine justices, a wall, wind, hot, cold, wet, dry, washed hands... everything is declared existential, to the point where wise citizens just tune it all out. Tom