American trainers who have worked with both the Iraqi and Afghan armies have noted some interesting similarities.
Homies- Both Iraqis and Afghans make good soldiers, but they are both very opposed to serving away from their hometown, or region. Definitely a homesickness problem here. Actually, it's deeper than that. In both countries, there is great disdain for the central, or even provincial, government. Government officials are seen as corrupt (too often true) and inefficient (also too true). For a long time, the only ones you could trust was your family/clan/tribe. The tribal organizations are particularly strong in both countries. The tribal elders are respected, not too corrupt (especially when dealing with members of their own family) and can be relied on for advice, dispute arbitration, and help in desperate situations. As a result of this, Afghan and Iraqi troops will often desert if they are away from their tribes for too long. This has to be taken into account by commanders. It means that you either have a lot of troops home on leave all the time, or that you take the entire unit back to the home base frequently, and forget about extended operations "out there."
Weak support- Neither country has the support services and facilities that American, and Western, troops take for granted. Logistics support is erratic, leaving troops hungry at times (and leading to looting, just to get fed.) Pay often does not arrive on time, or at all. Services for wounded troops and disabled veterans are poor. The governments don't look after the families of soldiers, which is another reason the troops want to serve close to home.
Corruption- Always a major problem in both countries, it gets in the way of serious attempts to solve all the other problems.
Culture clash- The troops who have accepted the Western way of doing things, do not get along well with the traditionalists. This tends to pit the younger guys (including junior officers) against older NCOs and officers.