The United States has always liked to keep a close eye on its neighbor to the south, making sure that things stay pretty comfortable for U.S. interests. But while former Mexican President Felipe Calderon enjoyed an especially close relationship to the United States, it wasn't enough to stop the NSA from hacking his email account and spying on his whole administration.

In yet another damning document released by Edward Snowden (this time in cooperation with Der Spiegel and Berlin-based journalist Laura Poitras), it is revealed that an operation named "Flatliquid" helped NSA agents "gain first-ever access to President Felipe Calderon's public email account." The top secret document details how the NSA could now spy on "diplomatic, economic and leadership communications which continue to provide insight into Mexico's political system and internal stability."

While it's no longer shocking that the spying was being done on a close neighbor and ally (which appears to be a common NSA practice), a surprising revelation is another set of documents that show how the U.S. was using the spying to steer Mexico's policy in fighting its drug war, as well as provide inside information to U.S. politicians and businessman.

The internal documents reveal that the spying was considered by the NSA to be a "tremendous success" and that "These TAO ["Tailored Access Operations"] accesses into several Mexican government agencies are just the beginning — we intend to go much further against this important target."

In previously reported leaked documents, the NSA was revealed to have monitored the text messages of then-Presidential candidate Enrique Peña Nieto during the summer of 2012. In trying to figure out how Peña Nieto would govern Mexico, the NSA boasted in a top secret memo that it intercepted 85,489 text messages sent by Peña Nieto and his associates.

All of this makes for a very uncomfortable relationship between the U.S. and Mexico. Not that U.S. leadership has ever given a second thought about what recent Mexican leaders want, but the NSA spying does reveal that they would very much like to know what they are thinking.