The IRG would head to the battle on the border while the "people" gathered up the despots in Tehran.
The Iranian army might not even leave the barracks.
Invasions have frequently had the opposite effect in that it has given license to the invaded country to crackdown on dissent. I don’t claim to know what would happen in the unlikely event that the US Army rolls, but I think that it is more likely to harden the Iranian response rather than weaken it.
Then your sitting there with a thin slice of Iranian territory an no “Plan B.” Iran is a pretty vast & rugged country.