I can see it playing out in various potential ways. The Iranian government does not have the populace on it's side, which may grease the gears during an attack. Many of the older world regimes are used to playing the slow game, going for territory, or attempted genocide, so a fast and hard approach may be too much for them to handle.

Russia has some boats going that direction, but defending Iran doesn't benefit them. Ukraine is a far bigger prize/goal, and they don't want to weaken their efforts there.

China is also sending boats, but they like to posture a lot. I wouldn't be surprised if their warships end up being wax-coated cardboard. Their strength isn't tech; it's their number of willing bodies.

Also, the US military likes to use weapons that it never publishes. With enough surprises, it could take what it's aiming for, then leave the shambles behind.

Of course, there could be other surprises from either military. Ultimately, one group of fear-filled elites has planned for the US to fall by engaging in a multi-front war, with China being one of the victors. However, their plans have failed in some cases in the past (like converting North America to using the "Amero" by 2010, as one example), so it's certainly an intriguing show.

I hope the Iranian people are ready for havok and chaos. If they're prepared, they may survive to rebuild from the remains. That would prevent millions from being killed, and death may be relegated to the participants.