Buy a camera that uses AA or AAA batteries, and when you get to the US buy a plug-in battery charger for US voltage. They cost about £15 here, so they'll be $10-15 in the US.
Other than answer above, you'll have no problems. Probably better off buying it in the US, as it'll be cheaper.
Buy a Sony/Olympus/Canon and you'll be fine. They seem to be very reliable bits of kit.