Why do you think this attrition would be one sided? Iran's infrastructure would be destroyed and it would turn into an Africa tier nation within the first week of its involvement. Unlike Israel, Iran can't defend its infrastructure. Unlike Israel, Iran's entire economy depends on easy to destroy oil infrastructure. Unlike Israel, Iran can be blockaded at the Straits of Hormuz.
If you delude yourself enough into thinking Iran can win a war of attrition with Israel, let alone the US, you're not worth talking to.
Iran already can't bring water to its citizens.
Hezbollah's involvement would turn into a civil war and would ruin Lebanon forever.
The same pictures you see in Gaza, where 80 percent of the population is displaced, would happen in Lebanon, except with much higher casualty rates.
I'll listen to you once you'll be capable of stopping our JDAMs