As with much military equipment of the late cold war the A-10 never had the chance to prove its capabilities until the 1991 Gulf War. I believe the plan to replace it with an 'A-16' variant of the Fighting Falcon had been underway before then, but after it showed what it could do in Iraq its place in the inventory was assured. I also think that had it still been in production at that point it may well be flying under other nations' colours today.
The USAF's argument that it would not survive in airspace where enemy fighters would be present is an odd one, as the same argument applies surely to the B-52, B-1 and AC-130, none of which are on the endangered list.