The United States was founded with respect for the recognition of world opinion. Knowing it's relative minority status in the world, it has sought to neither convey itself as neither an imperialist or an isolationist.
Furthermore, it initiated the establishment of the United Nations as a broader umbrella of the concept of "balance of power", which through the promotion of liberty and justice for all, would create a body of opinion which would normalize relations between "imperialist" and "isolationist" conflicts. Something which had destabilized the world throughout ancient history.
The United States, having begun as a minority and cherishing minority values, has only sought to promote peace and prosperity as well as conflict resolution. It has traditionally believed in a "live and let live" world.
If not for the United States, there would be no United Nations, which has traditionally been a body of divided opinion. It is upon this basis that those opinions would be free of all governing coercion, and limited to the free will and self responsibility of both nations as well as individuals. Any other purpose would nullify the belief that society is able to correct itself. i.e. the power of the people, individual citizens.