Frankly, many popular stories and grade-school lessons about U.S. History are myths that Americans have perpetuated throughout the centuries. In some cases, they may be half-truths, while in others, they just never happened.
How many of us learned about George Washington chopping down a cherry tree, and his being unable to lie about it?
It is possible that some of these stories have remained fixed in our culture because they produce good citizens, while in others, we relieve our guilt for real or perceived past transgressions. Whatever the case, these myths exist in great measure.