The USA apparently sees these little wars as investments or something. It's getting too expensive: cut losses and pull out the troops.
A real "USA loses" scenario involves the White House flying a foreign flag. A real defeat of the USA would probably shock americans to the core. Fully expect them to lash out with nuclear weapons if such a thing ever happens.
Is that and act of victory or defeat ?
Defeat is the US military getting routed and decimated. Defeat is US aircraft carriers sinking to the bottom of the ocean. Defeat is Washington getting nuked.
What actually happens is the opposite. Americans show up and inflict staggering casualties while suffering a relatively small anount. Then they suddenly leave for some idiotic reason like the president wanting reelection.
America's enemies don't need to actually win, they just need to resist as long as possible and drive up the costs of the war via asymmetric warfare.