Do you think there's folly in comparisons with an air war in which the circumstances and methods used were so different, though? The air war conducted over Vietnam bears little resemblance to how an air war would be conducted now - or how it was conducted in 1991, for example. I understand your point re the AAA threat, but I think it would be more instructive to look at AAA threats in Desert Storm or Allied Force, because the air war over Vietnam was fought in such a different way - for example, looking at the type of munitions dropped in Vietnam and flight envelopes necessary for their delivery, the environment in which they were operating and the limitations of sensor systems in said environment - wouldn't that be quite relevant as to why the AAA threat was as pronounced as it was? It's something to think about, anyway.
I think it's also worth remembering that the philosophy behind destroying an IADS, from the US point of view, is what's important in determining its effectiveness against Iranian air defences. Whether or not Iran has more potent air defences than Iraq, I suspect the methods by which the US approach IADS destruction is a more important factor than the size of the IADS itself, as if the method is sound then the amount of force applied by the US can be expanded to suit a larger IADS. I don't know if I'm putting it in quite the right way (it's early and no coffee) but the point I'm trying to make is that the capability to destroy an IADS shouldn't necessarily be judged solely on the size of the IADS but on the attacking force's ability to address the components of the IADS, and gradually dismantle them accordingly.
As I said above these are just things to think about - I don't know enough to say for sure, my thoughts are just straying in this direction.
