While I agree that the USSR was worse, the two absolutely are comparable.

• The US had concentration camps. Arguably it still does, just not for its own citizens.
• The US currently has inhumane and deadly prison conditions, but they used to be far worse.

Comparing deaths may put USSR on top, but the US isn’t that far behind.

Comparing authoritarianism is another story. Both quieted political dissent in the same way: raiding opposing political organizations and jailing or killing their leaders. That is authoritarianism.