You have a really strange way of deciding who won a war. Most people would consider those "vague political goals" the whole point of going to war, and the people killed undesirable casualties. But if USA really did go to war just for the sake of killing people, I guess they have indeed been pretty victorious. Much like Germans in WW2. I mean, they might have failed to accomplish whatever vague political goals Hitler had in mind, but they definitely killed a lot more people than they lost.

There is no peaceful war so obviously headcount is also a measure of superiority. Ever heard of Pyrrhic victory?

But it's largely a pointless measurement, unless your goal is the extermination of a population. Soviet losses on the Eastern Front were much higher than German losses, which didn't prevent the German from losing on that front.

Or take WWI, where the collapse of the government was the death knell for the German military effort.

On the Russian front this was only true at the beginning of Operation Barbarossa, then it became very clear a year later than the German losses became increasingly in Soviets' favor. Plus Soviets were fighting on their home ground, with direct access to resources, which would eventually turn the advantage on their side. Of course hindsight is everything, but several generals opposed Hitler's decision to go against the Soviets because they knew the odds were against them. So assuming that Germans expected to win is, I think, improbable.

And to come back on the original point, you do War to kill enough people to make your opponent give up or until it is completely destroyed. In the case of WWII, even if Russia kept losing soldiers 10:1 vs German soldiers, Germany would have still run out of soldiers to fight with anyway because of Russia's massive supply of men behind the frontlines - And even if Russia did give up at some point, there would have been no way Germany would be able to control a country as large as the Soviet Union with the army they had on site. Germans were clearly bound to lose no matter what.

I don't think anyone ever questioned the "superiority" of the US army. But whether that accomplishes the objectives of the war the the real question.

The goal was to prevent Vietnam from becoming a communist state supported by the Soviet Union. Vietnam became a communist country: that's a clear cut Soviet win and US loss. That US was not able to translate its technical superiority in a victory is very interesting (including with regards to recent wars), but doesn't change the outcome.

If you are talking about recent or ongoing wars (Afghanistan, Iraq, Libya or Syria), indeed the goals are much less clear, so it's hard to see how anything currently being done is really helping.

Why do you put "lost" and "wars" in quotation marks?

It seems to imply that because of the higher body count, we should consider the US the winner?

By the body count metric, the Nazis beat the Soviets.