“The idea is that because it can’t protect itself against front-line fighters, it always needs top cover. But don’t supersonic jet fighters doing CAS and strike missions in contested airspace have to have top cover, because it’s hard to focus on those missions and also defend yourself against enemy aircraft.”
After a few days of an air war, enemy air defenses, airports and aircraft are destroyed.
Our troops are deployed after establishing air supremacy. They can be closely supported by Warthogs and Apaches.
That's a given if you're fighting Iraq or Yugoslavia. Against a near-peer adversary, ground troops might have to defend or advance under conditions of air superiority (and perhaps local instances of air inferiority) rather than air supremacy (never mind air dominance). That's when an aircraft that can't defend against enemy fighters is either used, and shot down in large numbers, or out of the fight until air superiority can be established. While it would be nice to have a specialized CAS plane like the A-10 along with multi-mission fighter planes like the F-18 or the F-35, if push comes to shove, budget-wise, it's understandable that the Air Force would want the plane that can do both missions. The army has armor, IFV's, tube artillery, MLRS and helos to provide fire support. Only the Air Force can take on enemy fighters in hostile airspace.