I don't understand what part of American history is worthy of being idealized...
There was the part where we broke off of a powerful empire and formed a sovereign secular republic guaranteeing the rights of its citizens on the coastline of a mostly unexplored continent. And indirectly contributed to the start of the French Revolution by bankrupting the monarchy as they funded our rebellion to antagonize Britain.
Then again, there was slavery and killing off 90+% of the Native American population while pushing the survivors onto reservations.
Then there was the part where we put down a rebellion of our own people, partly because of said slavery, and in only two decades passed two amendments that took black Americans from slaves to voters.
On the other hand, the Civil War wasn't about ending slavery, and many black Americans weren't in a position to vote for nearly a hundred years after that, amendments notwithstanding.
There was the part where the New Deal vastly increased the lot of average Americans....
...and the part where federal agents and corporate lackeys gunned down unionizers in broad daylight.
The part where we fought three hyper-expansionist Fascist states at once for the survival of the free world....
...and imprisoned some of our own people for resembling them, followed by nuking two of the enemy's cities to try and end the war as painlessly as possible.
The part where we took up the position of the world's democratic superpower to hold off the spread of Communist dictatorships....
...but believed in Senator McCarthy and came close to ending human civilization in a rain of nuclear fire.
We don't really need to be idealizing anything, but that doesn't mean that there is not plenty of good to be found in American history, just as there as plenty of bad.