Is US 120v or 240v?

Someone told me the appliances for United States 240v, are combined with TWO 120v hot wires, a neutral, and a ground wire, like refrigerator? If yes, can it be power by one 240v hot wire (single phase), and neutral, ground wire?

There are very few appliances in the US that are 240v, most are 120V, with only the high current ones such as a dryer, stove/range, and some air conditioners. However it is unwise to assume that all 240v appliances only utilize 240v, many older units utilize one hot leg to ground (120v) to power the controls, so the safe answer is NO unless you have intimate knowledge of the circuitry and/or the manufacturer clearly states that it is permissible.

The 240 volt loads used in US residential appliances are typically clothes dryers and ovens/stoves. Some people will have 240v heaters and welders also. For these type loads, the receptacles are configured with three or four terminal contacts: 2-phase and one ground; 2-phase and one neutral; or 2-phase with 1-neutral and 1-ground. All connections require at least 2-phase terminal contacts. 240v loads are never connected with 1-phase and 1-neutral for residential appliances.

I have seen many modern appliances that have electronic power supplies that are dual voltage rated because they immediately convert the supply voltage to DC and are therefore indifferent to the configuration of the supply wires as long as the correct cord set is used, but you cannot generalize.