Topic: Do I have to buy American AC adapters to charge my 3DS and Switch in the United States?

I'm going over to the US soon, and I really want to bring my Switch and 3DS, but I'm wondering if I can charge them over there.
Here's some useful information:
I have an Australian 3DS and Switch. The Nintendo Switch AC adapter support 100-240V. My 3DS AC adapter supports 230-240V.
I purchased a third-party 3DS AC adapter from my local games retailer, and it came with the AC adapter (100-240V), and a USB cable. I also purchased a USB Type-A to USB Type-C cable for my Switch.
What I'm wondering is if I can charge my 3DS and Switch via the USB chords using the American voltage.
On the Nintendo Customer Service page, they mention to purchase an AC adapter in the country you are visiting (source: http://www.nintendo.com/consumer/systems/general/rechargeable...
Is that necessary for the 3DS if I have a USB charging cable? I really don't want to blow up my 3DS or my Switch.

Any help is greatly appreciated!
-Mr Kaos

Just plug a usb cable into a US plug. Done.

@gcunit Thanks. I wasn't too sure if that would work, but according to you and others, that seems to work. Thanks for your help!

You can also buy converters in most electronic and office stores here.

Buy a cheap phone charger there and the very cheap micro usb to usb-c piece of plastic.