Answer:
The sentence from Kennedy's speech that best aligns with the concept of people around the world to hold each other accountable is "Finally, whether you are citizens of America or citizens of the world, ask of us the same high standards of strength and sacrifice which we ask of you."
Explanation:
Kennedy wanted people to work and fight for a better future for all, to stop war and injustice and to be able to rely on each other without any kind of prejudice, this line exposes that message by saying "whether you are citizens of America or citizens of the world" he is getting everyone involved, doesn't matter who you are or where you are, you are part of the whole.