Blame the ITU & the USA: North America Frequency Plan
Frequency assignments are determined by the International Telecommunications Union (ITU) < http://en.wikipedia.org/wiki/International_Telecommunication_Union > which is an international forum.
Lucky Canada has to follow along with the USA frequency plans as we are so close. CDMA is also a world standard < http://en.wikipedia.org/wiki/CDMA2000 > although it is a fading star since it's major manufacturing proponent has ceased development on the chips.
All cell systems in North America use the N.A frequency assignments, as well as Japan. CDMA is also used in Indochina although Vietnamese CDMA carriers are switching to GSM.
Interestingly certain uses, such as maritime and amateur, etc., are uniform in all parts of the world.