The idea that America is unique among nations and has a mission to spread its ideals and form of government around the world is called .

American Exceptionalism.

Explanation:

A certain number of those who subscribe to "old-style" or "traditional American exceptionalism"—the idea that America is a more nearly exceptional nation than are others, that it differs qualitatively from the rest of the world and has a unique role to play in world history

both the address and the poster use diction to convey their message. diction is defined as a style of writing or speaking based on the types of words chosen in order to send a message. parallelism is when a similar sentence structure is used for several sentences on a text; roosevelt's address doesn't follow that. repetition has to do with repeating a word or sentence in order to emphasize and idea, however neither the poster nor the address use repetion. finally, the address doesn't use images to convey a message.

that is true because that is something they fulfill for their work.