Which nation did the Allies think posed the most serious long-term threat?
1 Answer
Most probably the USSR.
Explanation:
If you are referring to the Allies during World War 2 then I would say the USSR. During the 1930's there was considerable sympathy and support for Hitler in the West. Many industrialists such as Henry Ford actively supported the Nazis, who were seen as a bastion against communism. It also reflected considerable anti-semitism in the West.
It is also the case that within the USA there was a strong isolationist movement which existed alongside such anti-semitism and fascist sympathies. This was reflected in the fact that there was no guarantee that the USA would have declared war on Nazi Germany after Pearl Harbour.
In contrast the West was consistently opposed to communism and the establishment of the USSR from 1917 onwards. Even before World War 2 ended and certainly immediately after these divisions re-emerged with the division of Europe, Germany and Berlin.
