Iran isn't going anywhere. To the west are its enemies the US and Iraq. To its east are its enemies the US and Afghanistan. To the north and south are the seas. It may launch a few missiles, but it will never seize territory as long as the US is in Iraq and Afghanistan. It's pretty much boxed in, and there's little need for a US invasion of any kind.
"and there's little need for a US invasion of any kind."
Until it has its nukes ready for provision to every terrorist group known to man, for shipboard delivery to New York, Chicago (up the MS), San Diego, Houston, London, and points east.
Going into Iraq was 2 fold, number # 1 to get rid of a dictator threat of Saddam, and 2nd ? to sit and wait in what Iran will do.....