Answer:
The United States accepted its role as a world power after World War II, helping to rebuild Europe and Japan and taking the leading role in establishing the United Nations
Umm what grade are you in ?
The Soviet Union did this because they wanted to rebuild and expand their country after massive destruction and loss of life during the war. Essentially this aggressive expansion and annexing of these countries made the world realize that the Soviets were a massive threat to the world even though they were allies during WWII. I hope this helps :)
