To sum it up, regionally they are much like Toby Keith...not as good as they once was, but good enough once as they ever were. DIA sums it up nicely here:
"To achieve its goals, Iran continues to rely on its unconventional warfare elements and asymmetric capabilities— intended to exploit the perceived weaknesses of a superior adversary—to provide deterrence and project power. This combination of lethal conventional capabilities and proxy forces poses a persistent threat. The Islamic Revolutionary Guard Corps Qods Force leads Iranian power projection through a complex network of state and non-state partners and militant proxies. Iran’s conventional military emphasizes niche capabilities and guerilla style tactics against its technologically advanced adversaries. Its substantial arsenal of ballistic missiles is designed to overwhelm U.S. forces and our partners in the region. Its swarms of small boats, large inventory of naval mines, and arsenal of anti-ship missiles can severely disrupt maritime traffic in the Strait of Hormuz—a strategic chokepoint critical to global trade. Each of these forces are becoming increasingly survivable, precise, and responsive."
Most of their US equipment is not mission capable. This declassified CIA assessment from 1984 goes in to great detail, but the reality almost 100% of the F-14 fleet is not airworthy and the AIM-54s that went with the F-14 sale have long since gone past their shelf-life.
As mentioned elsewhere in this thread, there are essentially three areas of concern in the region. First and foremost is the anti-ship capability that could result in an actual or de facto closure of the Strait of Hormuz. While I think this has the lowest likelihood to occur, it does have the highest impact and, depending on how they close it, could be the most dangerous course of action.
Next, is the ballistic missile threat. This is worrisome in that Iran is capable of striking every major US troop concentration point in the area. The regional ability to defend against a full-on onslaught is limited and most of the damage wouldn't directly impact the nations in which those locations are. The counter is that the GCC member nations might get pissed enough to decide the Shiites are now crazy enough to justify a regional response, though I doubt that will occur.
Finally is the indirect paramilitary and terrorist organization threat. Iran can decide to go sideways, directing and supporting their proxies in a distributed fight against US targets. I see this as most likely course of action and so long as they stay away from political targets such as our embassies and instead focus on the smaller troop concentrations, the least dangerous course of action for the Iranians to take.
