Why would the berlin blockade cause a breakdown in relations between the usa and the ussr?
The blockade of Berlin was basically an attempt to force Britain, France and the USA into withdrawing from West Berlin. Initially after WW2, West Berlin was controlled by the US, France and UK. It later became part of West Germany (an ally)). The USSR, which controlled East Berlin wanted to control all of Berlin. The USSR stopped allowing supplies (e.g. food) into West Berlin by land. They could do this as West Berlin was completely surrounded by the Soviet controlled East Germany. That effectively meant that the USSR was laying siege to West Berlin and starving the people of West Berlin into surrender. During the blockade, the only way to get supplies into West Berlin was via planes landing at Schönefeld Airport in West Berlin.
