If launched from Iranian territory there is a pretty clear case for the US to go to war.
I know the “WW3” meme is popular right now but Iran is only a regional power and would likely lose a conventional war quickly against the US (matter of days or weeks).
Iran would lose control of their airspace pretty quickly and we'd be able to drop bombs on whoever we want, but there's no quick way the United States could occupy and control the country in that time (at least, not without resorting to weapons and tactics that would cause massive loss of civilian life, and which most soldiers would I hope refuse to carry out).
Some of the logistical issues are explained here: https://www.electoral-vote.com/evp2020/Pres/Maps/Jan06.html
Conventional War =/= Guerrilla War
Guerrilla Wars can go on for decades even with lots of boots on the ground.
This is going to get very interesting in terms of internal US politics. The Democrats don't trust Trump, including in terms of his motives and judgment in dealing with Iran. They also, in general, oppose war. They're trying to use the War Powers Act to reign him in. But if they do so, and prevent a response to this latest attack, that could cost a number of them dearly in the next election - especially since Iran is not likely to stop at firing a few missiles at two US bases.
I feel sorry for the poor fools who blindly follow the drumbeat of war and think they are doing a patriotic duty to their nation / meat grinder, which chews them up and spits them out once they are done with them.
But hey, Raytheon stocks are up!
We decided how much winning we wanted, and we did it. Unfortunately for the soldiers and the taxpayers, the politicians have a limited appetite for winning.
Vietnam is a fine example. We limited the amount of ammo! We didn't mine the harbor until very late in the war. The politicians ran the war as they desired, winning as much as they wanted to win.
In all those wars, the USA very obviously had the option for a quick and complete victory. It just wasn't done. Thank politics.