Why do Americans think they won the US war of indenpendence easily?

Time heals and makes events seem more distant. If you read the history books you'll see that the Americans did not win the war easily at all, and there were several times when they wanted to give up. That's why it lasted so long. In the end, it's very hard to keep control of a rebellious country that's very far away. That's been the case from the Crusades through the Vietnam War.