Your question is a rather vague and ambiguous question. The federal government holds the power for security domestic and foreign.
The Department of Homeland Security supported by other public safety agencies, such as the military, Federal Bureau of Investigations, and the Central Intelligence Agency work to ensure our public's safety by negotiations and establishing foreign relations through NATO and such.
If you could re-word the question then it is plausible you can find a more preferred answer.
Hope this helps.