I recommend Stephen Johnson's (former Deputy Assistant Secretary of Defense for Western Hemisphere Affairs under George W. Bush, now at the Center for Strategic and International Studies) take on Iran in Latin America. The conclusion:
A lot of what we think we know about Iran’s activities in the Americas is based on sketchy evidence, such as newspaper reports of a jointly constructed missile base planned for Venezuela’s Paraguaná Peninsula. Overstating the case for action could set back relations with friendly neighbors and make cooperation, when needed, less likely. Instead, U.S. and friendly intelligence services should boost efforts to understand the degree to which Iran is circumventing sanctions, transferring technology and materials, establishing an Iranian Guard presence, and engaging terror groups for possible attacks. Obtaining reliable information is a necessary step in mounting an effective defense. After that, maintaining links by offering a competitive relationship advantage, even with disputatious neighbors, is the best way to minimize the appeal of competing powers.
That echoes more or less my recent post on the topic. What people claim to know about Iran's activities in the region is based on weak sources. This does not mean Iran isn't doing anything dangerous, but rather we know much less than many people claim to know. This is really important when making policy decisions because bad policy can isolate the United States, which is the opposite of what we need.