no war since WWII, with maybe the exception of Korea, met the standard of a clear and present danger and resulted in unpredicted consequences. There is no arguing base on the facts, that the American people were purposely mislead by our political leaders for political reasons and that basis for waging war in both Vietnam and Iraq were both wrong and immoral.
ww2 warped the mindset of foreign policy though. Leaders from ww1 to ww2 didnt learn their lesson so they were unable to prevent another world war. Leaders now go in preemptively to avoid ww3.
So if the standard your looking for before going to war is a ww2 situation then you should be careful that you get what you wish for.