The post-WWII period and beginning of the Cold War (starting dates are somewhat ambiguous, though George F. Kennan's "Long Telegram" was posted in February 1946, and the Truman Doctrine declared on 12 March 1947) also saw an arms race, particularly of increasingly-powerful nuclear weapons (the hydrogen bomb was first tested in 1951 & '52), jet-powered bombers, and work was proceeding on what would be the first intercontinental ballistic missiles (the Soviet R-7 Semyorka, first launched in 1957), as well as the still-in-operation B-52 Stratofortress long-range strategic bomber (first prototype flight in 1952).

I've seen variants of Clarke's observation such as extrapolations of combat aircraft costs which lead to a single plane being shared amongst the US Air Force, Navy, and Army, with the Marines having dibs every few weeks, something similar.

The criticism isn't entirely fair, as there is an element to which a superior weapon or capability can utterly overwhelm numerically-superior forces, given an equivalent initiative to fight, and military leadership capability. The defence-offence advantage (that is, a defender virtually always has the advantage) means that yes, a technologically inferior force can wear down a superior invader over time, though shear weight of numbers (though often at immense cost), as with China over Japan in WWII (Japan occupied portions of the country but simply lacked the personnel to control all but a small fraction of it), the Vietnam against the French and Americans in Indochina, and Afghanistan against the British, Soviets, and Americans from the 19th through the 21st centuries. But at the same time in an initial assault phase technological supremacy can offer overwhelming advantage, as with the US in both Iraq wars and initially in the Afghan conflict, Nazi Germany against France in WWII (most notably radio-equipped tanks overwhelming the noncommunicative French forces), and presently in Ukraine where more advanced Nato munitions seem to be giving a critical edge over Russian massed forces and dumb munitions, though that's been a relatively closer contest, given that Russian leadership seems to have little concern for its own forces' losses.