Excited.
The message being sent to the world with the statement "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" is one of determination, commitment, and resolve. It conveys a strong commitment to defending and promoting the values of liberty and freedom, regardless of the challenges or opposition faced.
The audience's emotional response to this statement may vary, but the message itself is one of unwavering dedication to the cause of liberty. The audience's reaction could include a sense of determination, inspiration, or even a feeling of responsibility to support this commitment to liberty. Therefore, the audience might be more accurately described as "excited" by the resolute message.