Can the enemy really win in Iraq and Afghanistan by doing random bombings every so often?

I don't really understand that strategy. They do a small surprise attack every few days or every few weeks and the bomb mostly ends up killing a whole bunch of civilians. Their attempt at creating chaos and a full blown civil war has failed miserably, yet they keep trying. The U.S. troops currently win every battle they fight against the enemy in Iraq and Afghanistan. The enemy loses dozens and dozens of troops in every single battle (compared to almost no U.S. casualties) because they have no air force and they have very outdated low-tech weaponry. Their bullets can't puncture the bulletbroof gear that U.S. troops wear. They don't have night vision technology (for the most part). They also have no air defense whatsoever. They get completely slaughtered out there on the battlefield by U.S. bombs from planes and drones. The best they can possibly do is to kill a couple of troops every day (or month) with a roadside bomb. And the U.S. has adapted very well to these roadside bombs. The defense against these things is better than ever now. So how in the world can the enemy possibly win with this poor strategy? They are losing in the battlefield and in the battle of wills.