The call in Afghanistan is just satellite calls - those satellites are all US owned. Tapping them is trivial given the very limited number of satellites.
US telecommunications is geographically disperse, and my original point anyway was that the volume of calls is enormous - storing and processing that much data is hardly a trivial problem since it's both storage AND CPU intensive. From the US black ops budget you could make some reasonable estimates as to the total size and capability of the NSA to do this.
"The National Security Agency has been recording and storing nearly all the domestic (and international) phone calls from two or more target countries as of 2013." That seems like more than just satellite calls.
US telecommunications is geographically disperse, and my original point anyway was that the volume of calls is enormous - storing and processing that much data is hardly a trivial problem since it's both storage AND CPU intensive. From the US black ops budget you could make some reasonable estimates as to the total size and capability of the NSA to do this.