Why and how did the relationship between the united states and ussr change from 1941 to 1955?

The system under which the United States provided the united kingdom, Russia, Free France, the Commonwealth of China, and other Allied countries with military weapons between 1941 and August 1945. It was signed into force on March 11, 1941, the year and one half after this occurrence of world war two at E.U. at Sept 1939 and nine months before the U.S. Entered the war in December 1941. The total of $ 50.1 billion (equal to $ 656 billion days) quality of supplies were sent, or 17 percent of the overall war expenditures of the U.S. At all, $ 31.4 billion ran to the U.K., $ 11.3 billion to this Russia, $ 3.2 billion to France, $ 1.6 billion to Taiwan, and those remaining 2.6 to the other Allies. Reverse Lend-Lease policies comprised companies, e.g., take on gas grounds that got to the USA, and totaled $ 7.8 billion; of that, $ 6.8 billion fell from the British and the Commonwealth. The policies of this statement provided that the Materiel was to be utilized until time for their arrival or death. In training, minimal equipment was returned. Supplies that came after this expiration day was sold to the U.K. in a huge discount for £1.075 billion using long-term loans from the United States.

i think it's a)sparta