The band specs for the Aqua Ace are buried on this page in the "Connectivity" section. Comparing the listed frequencies with bands allocated to carriers in the US looks like there's no overlap for anything but 2.5g. FrequencyCheck.com is more user friendly, but doesn't have info for the Aqua Ace yet. However their other offerings mostly look like they'd be limited to EDGE or GPRS in America (except for the Aqua Super TD-LTE Dual SIM, which might work on Sprint LTE but probably won't be on their "list".) But again, I add the caveat that I'm just not that familiar with decoding this info and I'd really like to be wrong.