That's certainly the case with many companies in the UK, I think Apple were one of the few exceptions (at least they used to be) and if I was buying a grey import (non UK stock) I'd assume there's no official warranty with it.
Because the US is not a no fly zone.
There's no prohibition against flying that particular drone model in the country.
DJI just isn't releasing it yet because of
The problem sorting out issues around what to charge for the drone because of...
This was mentioned over on DPR, it's a camera system attachment Xiaomi were showing which uses a 100MB 4/3 quad bayer sensor:
https://www.gsmarena.com/xiaomi_modular_optical_system_concept_handson-news-66797.php
I can't find any sample images...