Why did the relations between the ussr and the usa change after the great patriotic war?

The USSR and the USA did not share each other’s views on the structure of society and politics. This led to a change in the relationship between them. The USA stood for the development of capitalism, and the USSR for socialism. After the war, during the implementation of the Marshal’s plan, the United States offered to help states to restore their economies, but on the condition that all communists were expelled from the parties. Many countries (not counting the USSR) agreed to this. The USSR decided to restore the economy itself, and then began to help other countries.