If there's is some space for an opposition (which your demonstration example implicitly assumes), there's some space for listening to non-regime media and organizations. Indeed, many people in Iran use Satellite TV despite it being officially banned. They may or may not trust American-owned TV, but there are plenty of alternatives.

If, for example, inspectors are not allowed to check for nuclear activity, the world would raise a ruckus and the average Iranian citizen will be able to hear it and evaluate the validity of these claims, even if the regime tried to hide it.

That said, I suspect the intention of the current American administration is to do a new deal with the regime, not to have the people rise up. They may wish for that scenario, but it's not something they are working towards or something they rely on in order to pressure the regime.

At the international level, the international corporations located in multiple countries don't want the different countries they're in going to war with each other, and so the massive leverage of international corporations in open markets provide an invisible hand of unseen forces that keep wars at bay.