Let this chinese prof sexplain
US cannot back orf. A bully cannot back orf as others will take advantage if they see US turning weak.
If US back off, arab states will appoint iran as their protector and pay protection money to iran.
russia will build a railway to iran ports to bypass european waterways.
china already has a railway to iran.
US cannot accept this. A new superpower in the making. Its going to be fight to the death or collapse of US hegemony.