You’d need a way to run HomeAssistant and some interface to talk Zigbee, like the Conbee 2 or the SkyConnect mentioned here. I was looking into purchasing the SkyConnect last week after hearing about this Philips Hue crap but am not convinced it’s the way to go, I found several reports of reduced range with SkyConnect compared to the Conbee. See for example https://community.home-assistant.io/t/conbee-ii-vs-skyconnect-performance/545759/2 or https://github.com/home-assistant/core/issues/86231. Personally waiting a bit before I purchase either option as I have a hub that works now, but leaning towards the Conbee2 at the moment.
There’s plenty of small cases or even 3D printable stuff available to put them in a nice enclosure. You could also buy something with an enclosure included, like the atom lite which I got some time ago as a cheap bluetooth proxy; https://shop.m5stack.com/products/atom-lite-esp32-development-kit
I have a lot of ESPs around the house but they are all in enclosures.
It’s in America so yes.