How were Sumerian social classes different from those in the United States?

This is an interesting question to consider given that Sumeria and the United States are separated by thousands of years of history and human development. Given that, there are vast differences concerning the social classes between the two civilizations.
We know from the surviving records of law codes of Sumeria that it had a highly stratified hierarchy of social classes. Unlike in the United States, laws applied to different social classes differently. Punishments could be different depending on which class the perpetrator and victim belonged to. In the United States, laws officially apply to everyone the same.
Social classes in Sumeria were also much more rigidly set than in the United States. The whole notion of "The American Dream" is that through hard work and determination, anyone should be able to improve his or her social and economic standing. This was not the case in Sumeria, which likely had very little upward mobility. In Sumeria, one's social class was determined at birth and usually remained the same throughout the person's life.
Another major difference was the role of religion among the ruling class. In the United States, there is a strict division between politics and religious institutions. This was most definitely not the case in ancient Sumeria. The king himself was the head priest of the civilization, and his closest advisors were also part of the priestly class.
Sumeria also had a slave class. While this was once also true of the United States, it no longer is, and this marks a sharp contrast between the two civilizations. Slaves in Sumeria were usually captives taken in battle, and they labored for the upper classes and wealthy merchants of Sumeria.
https://www.ancient.eu/article/680/daily-life-in-ancient-mesopotamia/