| | Re: UK to USA???
The 8520 will not (ever) work on Sprint or Verizon.
They use a different technology (as you noted) called CDMA which doesn't use SIM cards. Not weird. Just different. You also can't take a phone from another carrier and use it on Sprint or Verizon. "Unlocking" is not in their vocabulary.
T-Mobile USA uses different frequencies than T-Mobile UK.
My suggestion would be to visit authorized carrier stores once you move to the US and find out what the best model and deal is for you. Most important is to choose the carrier that has the best coverage for you as they are all different, and they have different voice and data plans.