A-Train, Do you think there are "just" wars? If so, then the USA has always been on the side of right and not might ...
I don't think the U.S. participation in WWII was at all unjust. I also believe that the intentions during WWI were honorable and generous, but with disastrous results, (namely, WWII). ALWAYS on the side of right? F*@k NO! The Iraq invasion was a moral and strategic disaster that is still hard for me to believe was perpetrated. Viet Nam? See below.
The particular Mai Lai massacre is an example of something that may not be specifically according to policy, but is the inevitable, predictable, and desired result of official policy that creates conditions allowing plausible deniability for those who make the policy...
Why were we in Vietnam again?
We entered under a fear-based, false premise called the "Domino Theory". Ignited by a pure lie called the "Gulf of Tonkin Incident". I was against that war BEFORE my brother served there for a year, came back to burn his uniform and medals and told us of some dishonorable inside realities.
But, the average American didn't support the war out of monetary gain or conquest. They truly swallowed the fear mongering that our political leaders served up. The truth of the matter took a long time to come out, but eventually, most of us figured out the ugly truths, swallowed our pride and withdrew.
The only place I differ with you a little is what I think is your premise that Americans didn't care about, or actually supported, the collateral damage you mention. I think the exposing of this is what turned Middle-America against the war. And massacres, rape, random murder has almost ALWAYS been a part of war. And I would argue that it SHOULD be. The old adage that armies don't go to war, but countries do underpins my statement.
But terrorism today is a different thing from the warfare I'm commenting on above.