The only explanation can be blind nationalism.
Nowhere else on Earth would deem an attempt at an invasion by a nation that ended up being invaded, as any kind of victory.
The US lost more soldiers and land to the British/Canadians in the war of 1812, and only got the land back after the Treaty of Ghent.
When the fight against reality is lost, it can only be realised that the US took a kicking in that war, and anyone American who can see it as a US victory must also be able to see the brigh side of a car crash.
