Because America was from the outset a nation of wave after wave of immigrants, so it had to create an identity which it did by telling a story which you learned at school, you read on memorials and you heard repeated in presidential inaugural addresses.
미국은 이민자의 물결로 생긴 국가라서 국가적 정체성을 갖는게 어려웠습니다. 그래서 학교에서 배우고  기념비에서 읽은 이야기를 말하고 그걸 대통령 취임연설에서 계속 듣죠.