Personally I don't see US facing any kind of nightmare scenario on the ground besides making the objective too large to where it requires a heavy number of ground forces which is not an option in 2026 as they need to be in ready state for any conflicts that can pop off with China and in Europe with Russia. Dedicating US manpower in Middle East is the biggest mistake that the US can't afford to do for those reasons.
Not because Iranian army is capable of inflicting massive casualties on US ground forces. I don't believe they are. US pilot being rescued from inside Iran is one example.
I'm not convinced that Iranian army can contend well against a modern military force with massive funding. Saddam's army couldn't. Irans army won't be able to defend coastal areas without AA, armored vehicles, control over their airspace, etc ....
The threat to US forces would mostly be mines/other anti armor + infantry weapons. Drones will not do much neither artillery against US forces.
Only reason they haven't considered taking Kharg Island, for example, is because neighboring Arab nations are not cooperating in acting as staging base for invasion.
Iran has prepared to its best ability to be able to absorb an US/Israeli attack plus retain strike capabilities on top of absorbing those attacks.
It did not prepare for a US limited ground ops in context of trying to actually repel such offensives. It cannot do that on those islands and coastal areas. The areas are large empty barren land and mountains. They cannot defend them without AA even with limited AA capabilities it would be a big struggle.
Instead they'd opt for trying to raise cost of such ops by striking at GCC infrastructure and maybe on Israel.
Trump is not taking ground op route because Arabs refuse to be a staging ground for that right now and US army and government is respecting that decision up until now.
Iranian asymmetrical tactics also helped it retain strike capabilities against region. Mostly GCC and Saudi area unclear if they have anything up their sleeves for Israel but they haven't used their maximum capacity. And they likely have a large capacity than what is known to public, but US army and government is aware of it of that probability and taking it into account.
Now if the resumption of war happens every few months while naval blockade and economic warfare continues, it's setting up a opportunity for limited ground ops in next year or two. However, there is no strategic objective to that if Iranian population doesn't revolt as US army won't be used for regime change war/occupation Iraq style.
Thus it may not happen at all. Netanyahu and Israel never had a credible regime change plan that doesn't involve dragging the US into a occupation regime change long term and costly war. Which is why Trump allowing them to start the war was a mistake as they were already cooperating on nuclear profile. Trump administration knew for a fact Israel doesn't actually have a credible plan for anything but still went ahead.
So we're back to zero where plan is now to get Iran back into a nuclear agreement deal but try to coerce them into giving up enriched uranium and any demand for sovereignty over SOH.