you can purchase a charger like the one you already got, but made for USA
i checked my charger (official from nintendo) and i was surprised that it only supports 220-240 volts.. because nowadays most chargers or adapters are made to support 110v-240v and you just have to find a traveler adapter because the plugs are different..
if you plan to move and don't come back, i would suggest to sell the charger and buy one in the US...
otherwise you can also get a usb cable and get rid of the problem (you just need a phone usb charger that supports the US current.. or charge the console on a computer or outlets that come with usb ports) ... however i do like to only use official accesories and nintendo doesn't provided a usb cable\charger... so you have to get one from third party