All-Powerful Image of the U.S. in Latin America

From Julian Assange:

U.S. intelligence agencies "can easily intercept these communications ... and therefore gain understanding of how Latin America is behaving, where it is moving, its economic transfers, the activities of its leaders and major players," he said.

"That permits the U.S. to predict in some ways the behavior of Latin American leaders and interests, and it also permits them to blackmail. Nearly every significant person in Latin America is blackmailable by the U.S.," the Australian journalist and transparency activist said.

There is something here I just don't get. If the U.S. is so all-powerful--more than we even thought--then why is it so unsuccessful at using the power? If the United States government could easily blackmail Hugo Chávez, Nicolás Maduro, Cristina, Néstor, Evo, et al. then why has it not done so? If it can see everything, then why does its actions not reflect that knowledge? If the U.S. has the power and simply chooses not to use it, then we are in an era of unusual and historic restraint, which seems unlikely.

Even during the Bush administration, when the NSA was in full swing, the U.S. government clearly did not know what was going in on much of Latin America. The U.S. was clueless about the intents of presidential candidates (who clearly qualify as a "significant person") like Lula and Ollanta Humala, which makes no sense if we were bugging their phones.

So I am skeptical. Believing this requires believing that knowledge is cluelessness, and information makes you less powerful. I'm not quite ready to make that leap.