ITU Callsigns - U.S.A.

Callsign blocks:-   AA-AL K N W.
ISO 3166 code:-     USA.NA
Timezone:-           (daylight savings time applies)

Amateur Allocations are as follows:-

KG4             = Guantanamo Bay - Cuba 
KH1 AH1 NH1 WH1 = Baker & Howard Is, Am Phoenix Is (CTE.OC)
KH2 AH2 NH2 WH2 = Guam (GUM.OC)
KH3 AH3 NH3 WH3 = Johnston Island (JTN.OC)
KH4 AH4 NH4 WH4 = Midway Island (MID.OC)
KH5 AH5 NH5 WH5 = Palmyra & Jarvis Island & Kingman Reef (PUS.OC)
KH5K AH5K NH5K WH5K = Kingman Reef (PUS.OC)
KH6 AH6 NH6 WH6 = Hawaii (USA.OC)
KH7 AH7 NH7 WH7 = Kure Island
KH8 AH8 NH8 WH8 = American Samoa (ASM.OC)
KH9 AH9 NH9 WH9 = Wake Island & Wilkes & Peale Island (WAK.OC)
KH0 AH0 NH0 WH0 = Northern Marianas (MNP.OC)
KP1 NP1 WP1     = Navassa Island
KP2 NP2 WP2 KV4 = U.S. Virgin Islands (VIR.NA)
KP3 NP3 WP2     = Roncador Key, Quita Sueno Bank, Serrana Bank/Serranilla Bank
KP4 KP5 NP4 WP4 = Puerto Rico & Desecheo Island (PRI.NA) 
KP5             = Desecheo Island

Broadcast Stations are allocated 3 or 4 letter callsigns.  Generally those starting with K are West of the Mississippi river and those starting with W are East.  There are however, many exceptions to this.  

Coastal radio stations are also allocated 3 letter callsigns and again K is used for the West and W is used for the East.