So you take Syria+Russias successes as well and fully attribute those to Iran? Iran was getting butchered in Syria before they called on Russia to intervene mainly in the form of air power. At the same time you guys used lebanese hezbollah to intervene.Go look at a map of Syria and look at the territory under Syrian rebel control and come tell me how much Iran backed Syrian government was defeated! You act like Russia was willing to get involved in the war without Iranian backed forces on the ground in Syria. You also like to act like the "rebels" were not getting all kinds of help from the Saudis ,Qataris, Turks... and even the U.S its self. What were all those foreign fighters doing in rebel ranks? do they count as "Syrian rebels"?
If any country was key to tilting the war in syria it was Russia due to the use of its air force to support ground troops. Syria and Iran have a none existent outdated air force.
If US attacked Iran I highly doubt it would be a full scale invasion. It would likely just be a large bombing campaign in which they would completely destroy your air force/navy/infrastructure in a matter of days. You cant compare yourself with the taliban. They fought an occupying force. You have a none existent air force, and your navy will be completely wiped. Dont forget what happened in Operation Praying Mantis.