Read this passage from Kennedy's Inaugural Address. What kind of rhetorical device is Kennedy using?

Let every nation know, whether it wishes us well or ill, that we shall pay any price, bear any burden, meet any hardship, support any friend, oppose any foe, to assure the survival and the success of liberty.

Repetition

Parallelism

Appeal to Authority

Antithesis

Repetition is used because they state several times that they would do anything. And the other two are not rhetorical devices anyway.

Parallelism

Explanation:

Parallelism is the name we give to the organization of ideas and expressions of identical structure. We have two types of parallelism: the syntactic parallelism, related to the terms of the same syntactic structure within a sentence; already the semantic parallelism, related to the similar ideas within a phrase.

The text presented in the question shows through several phrases that the nation will do anything to ensure the survival and success of freedom. These sentences are related to similar ideas within the text and this represents the Semantic Parallelism.