“we weren’t running around being the world’s police force”
Yes we were. I think Korea might have literally been referred to as a “police action.” Containment had more in common with policing the world. Japan attacked us largely because we slapped them for invading China and acting like we were the gatekeepers of the Pacific (ask yourself what out navy was found on Hawaii, anyway) . The Germans posed no direct threat to us, aside from to transatlantic shipping which was fine until it wasn’t, even though they declared war. We fought them twice more because they were supposedly guilty for starting it and were fighting it criminally.
You may be partially right about the congressional act part; I’d have to check Korea. But we haven’t declared war since WWII. Open-ended vague commitments held for Vietnam as much as for Iraq/Afghanistan.
Interesting that the Germans couldn’t make it 20 miles across the English Channel but supposedly posed a threat to us ...
I suppose one could argue there some sort of obligation to keep supporting the S. Vietnamese after Kennedy destroyed their government by letting Diem get whacked. Whether it needed to go so far as half a million US troops and 58,000 dead is another matter, IMHO.