Why did the wartime alliance between the united states and the soviet union unravel?

In spite of the fact that relations between the Soviet Union and the United States had been stressed in the prior years World War II, the U. S. - Soviet partnership of 1941-1945 was set apart by an incredible level of participation and was fundamental to securing the annihilation of Nazi Germany. The did wartime collusion between the US and the Soviet Union unwind on the grounds that the United States and The Soviet Union differ on the Future of Eastern Europe.