During the past decade, the NSA has secretly worked to gain access to virtually all communications entering, leaving, or going through the country. A key reason, according to the draft of a top secret NSA inspector general’s report leaked by Snowden, is that approximately one third of all international telephone calls in the world enter, leave, or transit the United States. “Most international telephone calls are routed through a small number of switches or ‘chokepoints’ in the international telephone switching system en route to their final destination,” says the report. “The United States is a major crossroads for international switched telephone traffic.” At the same time, according to the 2009 report, virtually all Internet communications in the world pass through the US. For example, the report notes that during 2002, less than one percent of worldwide Internet bandwidth—i.e., the international link between the Internet and computers—“was between two regions that did not include the United States.”
http://www.nybooks.com/articles/archives/2013/aug/15/nsa-they-know-much-more-you-think/?pagination=false