There’s a whole lot that can be done short of sending American troops. On our part, we could stop stalling on sending the Iraqis arms that they want to purchase with their own money. Step-up pilot training. Help them to launch their own surveillance satellite and drone technology. Sanction Arab regimes that are arming ISIS.
For their part, the Iraqis need to restore discipline and fighting spirit in their army, if necessary by shooting cowards and incompetents.
The Iraqi army spent the last decade knowing that if they didn’t do the job, Uncle Sam would do it for them. This had exactly the results one would expect (i.e. it made them weak and lazy).