Comment Re:You can just buy a sim (Score 1) 146
I have seen SIM card vending machines near the luggage retrieval at some international airports in the U.S.
U.S. phones aren't so much frequency locked to carriers - they are what they call "subsidy locked" to one specific carrier, but that happens when you purchase a phone from a U.S. carrier. If you are coming from outside of the U.S., and have an unlocked phone, then all you should need is the SIM card.
Some older phones had a more limited set of frequency bands - my old Motorola Razr was a "quad-band" phone that could work anywhere that I could find a GSM signal. But even older phones had fewer bands, which typically meant that they might not work in some locales.