It seems familiar because it was everyone's dream of America; and it was unique because only Rockwell managed to bring it to life with such authority. This was, perhaps, an America that never existed, but it was an America the public wanted to exist. And Rockwell put it together from elements that were there for everyone to see.
Rockwell helped preserve American myths, but, more than that, he recreated them and made them palatable for new generations. His function was to reassure people, to remind them of old values in times of rapid change.