There is no reason to limit anything that any American can do, which includes reading about a different country's heroes. If the comic is done in a particularly good way, it can also be an educational look into another country's hiustory and how the general public felt about the era.
Superman is not an American hero. He is a global hero. He even has a fortress of solitude in the North Pole. There is no value in creating a version of Superman where he is limited to saving Stalin in a foreign country. In the main story of Superman, he watches over Metropolis, a fictional city. Moving him to Russia makes him less relatable because of potential anti-Russian sentiment.
No, I do not think Americans should read a comic about Superman as a Russian hero for Stalin because Stalin is one of the most wicked men in the history of the world because he commanded the murder of millions of people during his reign in Russia. Superman is known as a hero that fights for peace and justice and his legacy should not be spoiled by Stalin.
No, I do not think Americans should read a comic about Superman as a Russian hero for Stalin because Stalin is considered one of the most evil men in the world's history because of the tremendous number of people her massacred. Superman is considered a good superhero and his legacy should not be tainted by Stalin, who was not known for good deeds.