At Chile’s Vera Rubin Observatory, Earth’s Largest Camera Surveys the Sky

Why do they do this? One of the political divisions is not like the others (one of them is also a colloquial name):

"which will be transferred and processed at facilities in California, France and Britain."

Keep it consistent, else I don't know what else you're playing fast and loose with.

France is the odd one out, right? California and Britain having in common that they're each only a part of a country.

Possibly because of the way things are set up (and then the journalist didn't think to clean things up). SLAC (California) is where the US-hosted data will be, but for the UK and France there is more collaboration between HPC/compute centres and so it may end up in different locations (I know for SKA the "UK" "node" is spread across 5 different institutes, so "UK" is a better description than listing 5 different cities).

That sounds plausible. Still, "Britain" isn't the name of any sovereign nation I know of. It'd be like a datacenter in Eemshaven getting attributed to "Holland." It's a bit sloppy. Also California isn't a country.