Once upon a time Persia had a democratic government. The USA and UK toppled it. Oil has dominated Middle Eastern politics ever since Churchill designated it as bunker fuel for the Navy.The Shah's regime was seen as an oppressive, brutal, corrupt, and extravagant regime by some of the society's classes at that time. It also suffered from some basic functional failures that brought economic bottlenecks, shortages, and inflation. The Shah was perceived by many as a puppet of – a non-Muslim Western power (the United States) The Shah's regime was seen as an oppressive, brutal, corrupt, and extravagant regime by some of the society's classes at that time. It also suffered from some basic functional failures that brought economic bottlenecks, shortages, and inflation. No surprise it was toppled.
The first rule of puppet governments is keep the people happy.It must also be pointed out that the US scored no additional brownie points by tacitly supporting Iraq during the prolonged Iranian Iraqi war. IT would seem entirely reasonable to me that the Iranian Government distrusts all US words and actions.