"Liberty Enlightening The World" or more popularly "The Statue of Liberty" has become the single most iconic symbol of the United States of America that I can think of.
The flag, the stars and stripes certainly gets its myriad uses, but often is subject to the whims of the politics of the day. The Statue of Liberty is more hopeful, more about the absolute ideals rather than the realities of American politics, in fact the Statue is not about the United States at all really but about the aspirations of the nation which holds possibilities for the world itself. The Statue which sits on Liberty Island (once Bedloe's Island - renamed one year before my birth) has been used by artists for as long as it has existed as a quick symbol of the U.S. and civilization itself. Popular culture seized on this and has made quite a bit of use of it, specifically pulp magazines and comics. Here are some examples from across the decades.