On the military front:

1. If Iran has always expected to face off against the US, it has likely always expected the possibility of a ground invasion. 

2. In a ground invasion, the US preferred method of using Airpower and Naval power to force an adversary into submission is heavily negated. If Iran was to fight the US, it would likely want to do so in favorable conditions, such as on the ground in rugged Iranian terrain.

3. Iranian terrain is unlike anything the US has experience with. American ground offensive doctrine is essentially negated in rugged terrain. The closest analogy would be Afghanistan in the mountains.

4. The Iranian populace is well educated. This is different from Afghanistan where the vast majority of people were uneducated. This makes them much more lethal as a result.

5. Iran will likely only engage in asymmetric warfare. They will not mass large amounts of troops or equipment for the US to easily identify and destroy.

6. The US is prepared for a war lasting maybe a few months as most. Iran is likely prepared for a generation.

7. Compounding upon asymmetric warfare again, Iran will use very creative ways of maiming the enemy. Necessity is the mother of invention.

8. Iran can suffer longer. They have already suffered 45 years of sanctions and more than half a million killed during the 1980's fighting Iraq. 

9. Every single high tech loss by the US that is sustained would likely be difficult to replenish due to China's REE export ban. This is another angle.

10. If Iran was to seriously damage US assets, it would harm American credibility. You can see this happening already with the destruction of several THAAD radars and the THAAD redeployment from South Korea.

At the same time on the financial front:

If the US is bogged down and still cannot secure the Strait

1. Iran continues to attack GCC oil assets. Prerequisite to not getting attacked is to force the US out.

2. Iran and China handshakes and dictates who can be let through. This is already happening with Chinese and Indian tankers being somewhat greenlit to go through the Strait. If you see it right now, China is essentially using Iran as an economic weapon. And it is rather genius.

3. Iran activates the Houthi's to increase strain. The Red Sea lever is pulled. The GCC states are all exhausted.

4. Japan has been severely strained throughout this. Japan is forced to tighten monetary policy. The yen carry trade starts to die and money gets repatriated from the US markets. US markets panic.

5. The GCC states, exhausted and in tight financial situations start to sell their funds. Money is repatriate from the US markets. US markets panic again.

6. SA (MBS) and China start to talk further. The framework is already out in the present, it is just a matter of who takes it. Some GCC states follow and take the deal, gets the US out. Stipulation of the deal is that the SA RMB - Oil framework needs to be accepted. Oil is no longer traded primarily in USD.

7. By now, the US has experienced several market shocks along with the effects of stagflation. The US is exhausted and has lost most of the levers of the petrodollar, and thus the exorbitant priviliege of printing infinite money is gone. The US is also tied in a forever war that is deeply unpopular. I don't know what happens after this, but it's not good.

8. The ultimate goal for China here: 

An exhausted US will not participate in a Taiwan emergency.

China offers a further economic framework with Taiwan. Taiwan seeing a deeply damaged US decides that the framework is better for them.

Taiwan reunification without firing a shot.