Ukraine's Attack Exposed America's Achilles' Heel

The "suddenly became capable" was a case of aircraft technology advancing substantially every year for decades, and several nations deciding to take advantage of that. Which was not easy to do - you needed a load of specialized aircraft, and weapons systems, and trained air crews, and supply pipelines, and command structure, and doctrine, and practice. Kinda like "we know how to kick a football", vs. "we are fielding a competitive professional football team".

"Unprotected" warships were, in general, not sitting ducks. But state-of-the-art anti-aircraft defenses were also non-trivial. Upside - those were relatively cheap. At least compared to losing your warships, or maintaining a combat air patrol.

Protective air screens (whether carrier-based or land-based) were again non-trivial. And America was particularly incompetent with those until fairly late in the war.