What caused tension between America and the Soviet Union after World War II

The main difference between both nations was their political views. America was and is a capitalist country and as we know has many freedoms. The Soviet Union on the other hand was a Communist country that gave no rights to its citizens. The United States wasn't happy with that. Also, after WWll, the U. S. provided aid to war torn European countries with the Marshall Plan but the Soviet Union hated this because they wanted to take over those countries.