Isn't the future in 3d printed automated drones, with absurdly low cost, that can saturate any defense.
So no, drones saturating defenses isn't a serious threat to nations or regional strength, only to very specific targets that are nearby (eg an aircraft carrier & crew dumb enough to park off the coast of Iran, after they acquire such drone technology, and assuming the US has developed no defense for such).
Also it is threat for exactly the regional powers. Iran does not care about US, it cares for Iraq, Israel, Saudy Arabia, Egypt and Syria.