That would be for an invasion.
We would have difficulty in occupying Iran and Iraq simultaneously. However, a large portion of our Air Force and Navy is sitting around twiddling its thumbs, and we could carry off an air war with few problems.
And now that I think of it, I'm no tactical expert, but it's possible that having thousands of troops, tanks, etc. in Iraq, just a road trip from Iran, might actually be more effective in running some Iran ground operation than if they had to be staged in from the United States like they were for Iraq.