I'm not American and I've never been there, but the impression I seem to get from my interactions with Americans (I have a penpal currently living in NH as well as a number of online Roleplaying buddies), as well as the ridiculous amount of American television that is broadcast where I am, is that any historic reference that does not present America or an individual who has been established in American history as a 'hero' is generally frowned upon.
Every country is guilty of trying to keep less flattering aspects of its history hidden from view, but one of my American associates recently informed me that she was actually kicked out of class once for mentioning that she believed the American armed forces had gone too far when they dropped atomic bombs on the Japanese cities of Hiroshima and Nagasaki. As far as her teacher was concerned, those attacks were justified by the fact that Japan had attacked Pearl Harbour. I was quite shocked to learn this; for one, Pearl Harbour is one city. And yeah, Japan was wrong to attack that city, given that at the time America had not engaged in any conflict with Japan, but in retribution America is justified in utterly destroying two cities, both of which are still suffering the long term consequences of excessive radiation exposure? That logic does not make any sense to me.
As a fellow historian, though admittedly not a professional one, I know all too well the frustration of people who only see one side of the story, and refuse to even look at the other side for no reason other than the other side of the story may well disprove what they personally believe.
Another common myth that I frequently come across is that Ancient Egyptian royalty was in the constant habit of incestuous relationships. To someone who has not looked at Ancient Egyptian history, politics and religion too closely, this is a fairly reasonable assumption to make, but it is completely false.
According to folklore, the Goddess Nut bore five children; Osiris, Isis, Seth, Nephthys and Harmachis. Osiris, the eldest, became Pharaoh and made his sister Isis his Queen. He also had an affair with his youngest sister, Nephthys and both women bore him one son each, but as Isis was his wife, it was their son Horus who was considered to be his heir.
Every Pharaoh, according to Egyptian law, had to make sure his or her (for there were several female Pharaohs) right to the crown was legitimate and watertight. Most did so by marrying either a sister or a daughter, but there is little evidence of these marriages being any more than a political alliance; the Pharaoh could 'justify' his position this way as he was married to a woman who bore the title 'Daughter of Pharaoh', whether this was his own daughter or a daughter of a previous Pharaoh. Very few of these 'Daughter of Pharaoh' wives are known to have had children in these marriages and in many cases the marriage was only temporary, with a divorce occurring so that the 'wife' could later on marry properly, usually into a union that would benefit Pharaoh in some way.
It wasn't until the Ptolemaic dynasty, the very last dynasty before Egypt was assimilated into the Roman Empire, that incest became a habit. The simple fact was that during this time Egypt was ruled by Greeks who could not speak or read Egyptian. They saw these political brother-sister marriages and assumed that they were marriages in the 'traditional' sense, and copied what they thought the Egyptians had been doing. This was also the most turbulent and dangerous period to be a royal, with members or the Ptolemaic family constantly contriving and conspiring to get their own relatives out of the way, usually by murder, sometimes by seduction and trickery. But that's another story for another day.