Iran has a very backwards military with almost no air force and no serious navy power at all.
The few planes they have are mostly ancient and their navy consists of speed boats.
They have a thousand tanks that are a mixture of ancient and more modern tanks with medium capability compared to the US.
They have a large standing army that is moderately well trained, with some large elite forces, and they have good ballistic missile capabilities. They have almost zero ability to properly defend their territory from the US when it comes to air strikes. They have almost no ability to keep up a foreign strike outside of their borders, with their ballistic missile stockpile being their sole means. Basically they have almost no ability to sustain foreign strike capability via their military. Outside their borders they have numerous proxy terrorist organizations they fund persistently for asymmetric warfare.
That's all they have. They're an impotent military after decades of sanctions and grinding poverty. In a war context that of course doesn't mean the US would find invading to be easy (it would be a disaster), it means the US strategy would properly be to sit outside of their borders and destroy everything inside of Iran and never invade; acquire air dominance (would take one or two weeks max), and continue wiping out all infrastructure and military capabilities as needed.