I found this on an old airpics forum... don't know how accurate, but it makes sense.
Has to do with the old (1920' and -30's) radiotelegraphy country codes.Countries were given blocks of one or two-letter combinations to assign to radiocommunication and telegraphy.USA received K and W,maybe others,Norway received the range from LA
.Norwegian fishing vessels even today have radio callsigns like LA
-PS,LA-KB,etc.Norwegian airports were coded LAZV (Sola),LAFB (Fornebu),etc. LN
is the code for airplanes.With the introduction of the MOTNE-network in Europe in the second half of the -50's,LAZV and LAFB became the present-day ENZV and ENFB.
Canada was a British colony and probably used a single letter given to Britain plus a three-letter code beginning with Y.When Canada became independent,it received the country designator C and kept the Y-combinations.Hence the ICAO designations CYUL with corresponding IATA code YUL
In the USA,airports in the ICAO system are coded KJFK,KORD,KLAX,etc.IATA:JFK
. Radio- and TV
-stations begin with K and W,followed by three letters.