It was invoked after 9/11. As for Iraq specifically I doubt it.
If I remember correctly, NATO gave air patrol assistance for the US, but then the United States decided not to use the NATO defense clause to go to war in Afghanistan and Iraq and opted for the “coalition of the willing” instead.
Perhaps the US did not formally request for the help out of fear the Europeans would turn us down and plunge the treaty into crisis.
The other possiblity that I could see is that the US did not want the Europeans to have the satisfaction of claiming for decades that they had to bail the US out of trouble even though everyone knows the US would do the heavy lifting.
If you don’t formally request for help under the treaty, I don’t see any reason to throw the treaty out. The problem with NATO, that I can see, has nothing to do with 911, Iraq, oil or Afghanistan. The fact is that European forces are too weak and out-of-date to fight along side the United States. Even if they were willing to go to war, they would have to be isolated by themselves on specific missions as to not interfere with US troops.
My understanding is that the UK is the only Western European power that has night fighting expertise. The other Euro forces are more comfortable with daytime fighting.