That agreement is functioning perfectly? Feel free to educate me on that.
By all accounts Iran was in compliance with the agreement and then Trump ripped it up. I think there are zero good faith arguments for doing what he did there.
Was the agreement perfect? That's the wrong question to ask because perfection isn't really the goal or achievable in diplomacy, or really any aspects of life. It was better than nothing, Iran was cooperating and it could've led to a better agreement by both sides showing good faith and keeping their word. Now all bets are off once again
Again, war with Iran would not be a traditional "conflict" or war with boots and tanks. It would be the US pancaking Iran (or more specifically Tehran). Yeah there would still be pain on the US side and elsewhere, but it would mostly stem from Iran blowing up as many oil fields in the middle east as they can. But Iran also knows this isn't going to happen over an outdated and soon to be replaced drone and a Japanese oil tanker.
I'm not sure how you'd just "pancake" a country with an aerial campaign using conventional weapons. I'm not sure how you have boots on the ground without the potential for tremendous casualties. It seems like Iran is far more capable than Iraq was and look how that turned out? It's one thing to roll into Tehran and topple the government in a week or something like that, but the ensuing power vacuum and I'm assuming occupation would be a nightmare