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US homes have both 120 and 240 in them. Its 3 wires from the pole. The pole transformer is 240 volts center tapped. The center tap is connected to earth ground.
Most devices in a US home are 120. Heavy power devices are 240 such as electric clothes dryer, hot water heater, air conditioner, electric stove.
Most post war (WW2) homes were wired that way from the beginning.
NOW, the commercial/ industrial industries use a variety of voltages. 277 is common for large lighting systems.
208 (3 phase, 4 wires) is used for large motor devices, air conditioners, etc.
And then there is 460 (3 phase) that's used for high power radio and tv transmitters and such.
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