What has been the main reason for the high degree of tension between the united states and iran in recent years?

Nuclear power

Explanation:

In recent times, the United States and Iran have not had good relations at all, in fact their relations are mostly based around tensions and disagreements between the two. The main reason behind this is that the United States do not want Iran to develop nuclear power because it might use it for development of nuclear weapons as well. Iran on the other side is firmly standing on its development of nuclear power because it considers that every nations should have the right to do so, not only few to have that advantage. The United States have forced numerous sanctions on Iran because of this in order to damage its economy, so understandably Iran was not pleased at all.

"the attempts of the proletariat to rise above this abasement"