*Intervening* in World War II
Japan bombed Pearl Harbor, so the US declared war on Japan. Hitler was so delighted by this that he declared war on the US. It was on that basis that the US intervened.
Contrast to now: A terrorist organization with large camps in Afghanistan attacked the US. After the host nation refused to cooperate, the US and many many allies invaded Afghanistan to disable the terrorists.
Iraq did not declare war on the US, and it was not implicated in the attack on the US. The US said Iraq had weapons of mass destruction, which still have not been located, and on that basis invaded Iraq, which, unlike Germany, had not declared war on the US.
The comparison doesn't hold. It's a brave new world out there.