Shaheds and quads offer no threat to US air superiority. Iran can fling them at the ground targets willy-nilly, sure, and that will inflict causalities on FOBs and ground forces. There's no ready-made solution to low end attack drones. But the sky is going to remain with the US. This allows US to dispense JDAMs at anything that pops its nose out into the open. Which doesn't play well with the notion of "positional trench warfare". Any "position" like this is a liability when the kill loops are tight and the sky speaks precision munitions.
If a major ground operation happens, I expect it to look closer to "2024 Gaza urban warfare hell" than to "2024 Ukraine open field war of attrition". Defending forces hiding from the air power in urban formations, causalities and collateral damage from the attackers trying to flush them out, humanitarian consequences from supply lines interdictions.
I very much agree that "the war is unpopular in the US" is a severe pressure on how much US can accomplish in practice. But what US sets out to do, how hard the US commits and how much can US actually accomplish there all remain to be seen. They could well purge the regime, destroy the key weapon facilities or grab-and-hold the oil fields before the domestic audience runs out of patience and pressures the politicians, or votes the decision-makers out.
Keep in mind: Iran isn't running off a pool of limitless resources either. The regime was already struggling a lot before US and Israel declared open season on the leaders - and the external pressure only buys you this much cohesion. Iran's military infrastructure is not in a tip-top shape, their income streams are dubious, they don't have many allies left after the proxy purges, they don't have reliable weapon suppliers overseas, and their own weapon stockpiles and production are unlikely to be sustainable in any way. They can sustain much more manpower losses and tolerate more hardship, sure - but there is no limitless tolerance. A regime that purges protestors by the thousands can't rely on its population being willing to suffer and die for it.
So there's nothing inherently "unwinnable" about this. It's a horrid mess of unknown war goals, questionable decision-making and dubious war sustainability, on both sides. Outcomes are very hard to estimate without some damn good intel.