Nearly all international HSPA+ devices work fine on AT&T's HSPA+ network and MVNOs that use the same network, such as Straight Talk's bring-your-own-device SIM plans.
More and more international HSPA+ devices are now supporting AWS1700, required for T-Mobile HSPA in most areas.
Sony has not released a CDMA device in quite some time. However, Qualcomm's latest modem chipsets make doing so far more feasible than it has been in the past, so a Verizon variant is possible. However, a Verizon variant is going to be heavily locked down.
As long as you are on Verizon, you will be stuck with inferior locked down devices. I suggest leaving them for Straight Talk as soon as you can.