America should not have attacked Iraq in the first place. You cannot win against terrorism/guerrillas using conventional warfare. Pretty much the same will hold for Yemen. You get stuck in an endless fight turning a whole population against you, anyone of them becoming a potential terrorist. Conventional warfare tries to win territory. Terrorism/guerrilla warfare wants to win populations to their cause, either through fear/hopelessness/fatigue or through propaganda.

The only way I can see to fight Al Qaeda is using espionage and friendships with (non-militant) Muslims to find the terrorist cells and then using special forces teams to take them out, leaders first. Choose these friends so as to not make you more enemies, though. Pour money into propaganda and financial aid to the peace-loving "common people" of the areas where terrorist groups might find help or potential recruits. Build/support schools with pro-western values. Not as spectacular and probably won't score political points at home, but much more effective in the long run.