Iran is a regional power, obviously they're going to be a threat to Jews.
The other problem is that Iran also wants to be a leader of the Muslim world as a way to exercise soft power, even though most Muslims hate them and consider them to be infidels. So in order to score brownie points with other Muslim states, they have to be really vocal and gung-ho about fighting Islam's external enemies - hence the unceasing seething about America and Israel.
Before Dubya called them the Axis of Evil, Iran called America The Great Satan.