If the douchebags running the show decide they want to commit to a full-scale invasion with all available assets,

If you've played RTS/starcraft, zerging one unit at a time after you have started the campaign, is not effective. Zerging as a verb also refers to suiciding cheap units to overcome a big objective, and US is not playing the Zerg side. Putting entirety of US military forces in near proximity of Iran is going to continue the reported hospital filling Iran strikes on those gatherings from this weekend.

The plan you speak of is completely different than surprise assassination of ayatollah followed by quick air campaign hoping for surrender. It is something that has to be in place before the air campaign, and not one unit at a time that has 2 week lag time before it is in position.