That must upset the Scots, Welsh and Northern Irish.
I wasn’t quoting wiki… here’s the list from the UN:
https://www.un.int/protocol/sites/ww…fcountries.pdf
You’ll notice that “Switzerland” does not exist on that list. That said, the Swiss Confederation, does…
Similarly, ISO 3166 lists “the Swiss Confederation” as the full name of the country:
https://www.iso.org/obp/ui/#iso:code:3166:CH
ISO does list Switzerland as a “Short name”
Based on that, I would postulate that Swiss as an abbreviation of Swiss Confederation, (same as America for the USA), is equally valid.