Meant to comment earlier, but I was timered for posting porn XD
So here goes
Indeed. Most wars in American history have been mistakes, IMO. But World War II was not one of them.
Few countries had the capability to stop Hitler from achieving his goal of conquering a huge chunk, or all, of the world and turning into a police state where all dissent would be squashed and non-Aryans would be enslaved and eventually massacred.
The U.S. and its allies (most notably Britain and the USSR) fought on the side of righteousness against Nazi Germany and its equally depraved allies, most notably Imperial Japan.
Perhaps Hitler could have been contained through smarter diplomacy and better decision-making in the 1930s or even going back to the end of WWI (imposing a more just peace on Germany that did not leave them mired in an economic depression that caused desperate Germans to turn to a strongman like Hitler).
But those are historical counter-factuals we’ll never know the answer to.
The Civil War is another example of a “just” war from the Union’s perspective. Reclaiming traitorous breakaway states that aimed to set up an apartheid slave state.
The Afghanistan War was (at least initially) justified to defeat Al-Qaeda, the perpetrators of 9/11.
But circling back to what I said upfront, most wars, particularly in recent American history, have been mistakes that can basically be chalked up to the fallacy of having a hammer (the world’s most powerful military) and therefore viewing all the world’s problems as nails.