Answer: Alliteration
Explanation: John Fitzgerald Kennedy became the 35th president of the United States of America on 1961 and died of gunshot wounds during an assassination attempt in Dallas, Texas before the completion of his tenure in 1963. John Fitzgerald Kennedy's inaugural address(speech issued by an elected leader usually during a swearing-in ceremony, where he makes his intention known to the people.) usually incorporates many rhetoric elements.
The phrases ; "whether it wishes us well or ill," , "struggling to break the bonds of mass misery," and "the survival and the success of liberty." demonstrates the use of ALLITERATION, which is the repetition of consonant sounds or letter at the beginning of words that are adjacent or close to one another. It helps to aid remembrance and raise the mood of audience due to the repetition of sounds or letters.