One area where it does not work well at all is modifying photographs of people's faces.* Completely fumbles if you take a selfie and ask it to modify your shirt, for example.
* = unless the people are in the training set
Sounds like it may be a safety thing that's still getting figured out
The Americas are quite a bit larger than the USA, so I disagree with 'american' being a word for people and things from mainland USA. Usian seems like a reasonable derivative of USA and US, similar to how mexican follows from Mexico and Estados Unidos Mexicanos.