Soviet Union was a state capitalist society with totalitarian government. That is, all means of production were controlled by the state. No private ownership allowed. Internationalism was a basis of Soviet national politics.
Fascism is a radical nationalist ideology with a mixed economy when privately owned means of production isn't a problem .
Communism is a stateless society with commonly owned means of production. Stateless implies no borders; all countries are cooperating and benefiting the whole planet, not a particular nation.
That means, the USSR wasn't communist, but it wasn't fascist. The perceived similarity with fascism is totalitarian government, though there is a difference: Dictator (Führer) in Germany had enormous personal power while the USSR was controlled by elite (Nomenklatura).
