The US system is split phase, 120VAC-0-120VAC.
As far as I know there are three different types of US sockets:
- Two pin - 120V only, no earth connection so class 2 appliances only.
- Three pin - 120V with earth.
- 240V - two lives each 120V and one earth.
Most of them will probably be 120V three pin, 240V is only used for high drain appliances like cookers, airconditioning and clothes dryers.
If you use a 240V socket, you'll need a double pole switch and two fuses if you need to protect against live to earth shorts.
How much power does this appliance use?
If it's fairly low power say <500W then a set up transformer is probably your best option, if it's high power then use 240V sockets.