The problem is that at the time the modern cell networks were being built in the USA, two competing digital network technologies were vying for control of the digital cell phone network market; GMS and CDMA2000.
Technically speaking, CDMA2000 was in fact the better network technology at the time when it was competing with GSM.
Now, we have to go back in time a bit for this story so let's take a trip down memory lane.
Back when the modern cell networks in the USA were being build, what was once known as GTE (which later became what we know as Verizon Wireless today) was building the networks. CDMA2000 proved to be a better standard to use at the time because it required less capital expenditures to deploy a network to sufficiently cover an area due to the fact that CDMA2000 networks didn't require as dense a network build-out as GSM required. So from a capex standard, CDMA2000 was a win for the then GTE.
GSM requires a much more densely deployed network than CDMA2000 thus required more capex to handle the same amount of traffic that a CDMA2000 network could handle.
So now you have the reason why carriers such as Sprint and Verizon Wireless have CDMA2000-based networks.--
Tom's Tech Blog