Can be used directly in USA electricity, because working voltage is 110V / 220V , so you can just put this bulb in any B22d or to E26/E27 socket lamp with adapter that included with lamp. Actually bulb have integrated resistor 3.3kOhm, so its working under both voltages, but initially its for 110V.
Disk inside tube will glow if connect to 110V/220V, if light it with Tesla coil - will be glow all the gas inside bulb but not a disk.