The correct answer should be completely
That's because if it got destroyed, it is already amused that it is complete destruction, since something can't be destroyed just a bit.
The correct answer to the complete sentence is <u>antagonism.</u>
Antagonism (noun) being by definition as an active hostility or opposition, as between unfriendly or conflicting groups can relate to this sentence since it mentions the two opposing groups as the Americans who thought we should stay out of World War II and those who thought we needed to stand up against dictatorship.