Explain why the usa-ussr alliance had broken down by 1947

One of the major reasons why the usa-ussr alliance had broken down by 1947 was because the US and USSR had very different political and economical ideologies, and the only thing keeping them tied together had been World War II, which had ended in 1945. 

The USA-USSR alliance had broken down by 1947 are discussed below.

Explanation:

The USA-USSR alliance had broken down by 1947 because of many key facts such as:

Difference in Ideologies United states follows Democracy while on the other hand USSR followed Communism.Suspicious Russian intention.The Communist government in Eastern Europe.The emerging threat of the Nuclear bomb.