You are taking a very unimaginative approach at the problem by mirror imaging the Ukrainians for the USAF. The USAF has been practicing SEAD since Vietnam and no one does it better. Any campaign vs the Russians first and foremost will concentrate on achieving air superiority and suppressing air defences.
Once that is that, CAS with F-16s from medium level is feasible, if needed, because an air interdiction campaign against Russian supply will come first, say goodbye to bridges, including the Crimea one, and tell me how Russian air defence units can be resupplied (those that survive). This wasn't a factor in Serbia because the supplies were decentralised or the firing units could re-supply in a night, but in Ukraine the distances won't allow that.
That doesn't even touch on other possibilities, like cruise missiles, EW and drones.