it's because the USA model will get the snapdragon 835 and its by the company that ownes CDMA technology and won't have to pay Qualcomm royalties for CDMA.
if it wasn't for Verizon stuck on CDMA Samsung would just use it's own soc on all the phones.
buying the snapdragon and using it in the states is cheaper than building there own soc and paying Qualcomm for a standalone modem and or licensing CDMA to use on the Shannon modem Samsung has built.
Nice info. So I'm assuming if they have an unlocked S8 it will be GSM only? I'm not sure how the S7 worked and if it was the same. Too bad because I am on Verizon.