They should have gone after Al Qeada in Afghanistan and Saudi, and wiped them out - making sure they actually got the perpetrators. Remember Osama? He's still at large and active.
Iraq had nothing to do with that attack, so should have been left as was. As you say, the war is illegal, so any retribution because of it is seen as justified.
As for Israel, the attacks there are horrific, as was the counter attack. They are steeled by their American counterparts, and feel themselves above the law - the attacks on civilian targets show this, but it's further underlined by the apparent deliberate shelling of the UN.