A number of question marks, still hope to be resolved...
Iranians Created Confidence Deficit from the beginning...
Suspension requirements by the UN, were not honored; even though Iran claimed that they did not need elevated enrichments... A measure of distrust goes at least a half of a century; shared by many Western countries who (too) have shared the behaviors of Iran...
It has not been only a US concern; it has been the concern of dozens of countries; just as it was not only the Iranians who signed the Non Proliferation Treaty.
Stability of the region amidst Lebanon, Palestine, Iraq, & Afghanistan, dictate the serious need for FULL International trust...