Yes I think you are misunderstanding. The leaner forces in all of the cases above are not the US, but the opposition.

Politically, not militarily. Same in Afghanistan. US could and did easily win the conventional parts of both conflicts. They lost because they didn’t know what to do after that or didn’t want to escalate it into a full scale war (Vietnam).

The US might have lost lots of wars but it is a clear winner in the propaganda front (at least until recently). The parent is a manifestation of that.

No, you both misunderstood what I said. Lean forces win. The US isn't one. My question is why then does the US waste on bulky investments.