Iran's resources are very limited. They simply do not have the capability to move on as many fronts as you're describing.

They also can't just let the US destroy their entire navy and air force and just shrug their shoulders with a "well, what can you do?" If a foreign power declares war on you (by invading and killing most of the people in a division of your armed forces), you're going to need to fight back - even if you're not going to win, there's no way an Iranian government would refrain from doing anything.

Iran's got one of the most powerful militaries in the region (behind Israel, maybe Egypt). They're going to counterattack. The US' largest footprint and assets are the various permanent bases in Kuwait, so that's the most likely response. They'd ask for (and probably receive) permission from Iraq to cross the Shatt al Arab and enter Kuwait over land and engage with U.S. forces there. Depending on how helpful Iraq wants to be, they can even allow Iranian troops to amass within Iraqi territory and advise the US that they are forbidden to enter Iraqi airspace - something that the US might have to honor.

The Iranian infantry wouldn't have much support - the US can dominate their air force, and in this scenario their surface Navy was destroyed (though they have a few dozen subs). But Iran will be alight with nationalistic and patriotic fervor, having had their brave soldiers murdered by the imperialist US without any direct provocation (they'll be the Ukrainians in their version of the story). And by turning up the temperature along Israel's northern border, they can keep their military occupied up towards Lebanon instead of having all their resources available to harry the troops along Kuwait.

It's not great for Iran to get into a shooting war with the US (okay, massive understatement) - but among their options in response to a massive attack from the US, that's probably their least-bad choice. They could also attack US forces in Iraq, but that's probably not a sufficiently large response to the provocation.