It was called isolationism :D
Answer:As World War II transformed both the United States and the USSR, turning the nations into formidable world powers, competition between the two increased. Following the defeat of the Axis powers, an ideological and political rivalry between the United States and the USSR gave way to the start of the Cold War.
Explanation:
I believe there are lots of reasons why the Roman Empire declined but the 3 most important ones are, Government corruption and political instability, Invasions by Barbarian tribes, and The rise of the Eastern Empire, but the one I think is the most important is the first one reason.
The answer would be necessary.
I believe the right answer is the Thirty year war. Hope this can help :-)
