Scott D has it in a nutshell:
The coalition forces cannot be defeated. They cannot be conquered in the field, they cannot be vanquished. They cannot be cut off and forced to wither away due to lack of supply, and there is no tactic or stratagem that is effective in dealing with an American military force.
The average person being spoon fed their opinions via media outlets might ask, if our forces are so clearly superior, and the enemy has no chance of victory over our forces, then how could we possibly lose? Easily. We have a huge portion of the population unwilling to face any kind of adversity. And this is not just about Iraq--it's an ingrained personality trait in many of our fellow Americans that affects many other aspects of our society. For all our defender's courage, skill, and dedication, the international community--and our enemies--know something about the American people: When we bleed, we leave.
As I've noted before, the tragedy in this is our weakness, acquired sometime after WWII (after Iwo Jima, after the Bataan Death March, after the Battle of the Bulge, etc.), is manna for the Bin Ladens of this world. They prick us enough, we deflate. They're not lions, they're jackals -- and we repeatedly allow ourselves to be left for dead, ripe for their pickings.