Switzerland was a country in the European continent of Earth. Cities included Geneva, Saint Moritz, and Zermatt. (Star Trek IV: The Voyage Home; TNG: "The Neutral Zone"; ENT: "First Flight"; DIS: "The Galactic Barrier")
When Data had traveled back to 1893 and claimed to be a Frenchman, Samuel Clemens mistakenly referred to him as from Switzerland. (TNG: "Time's Arrow, Part II")
In 2032, Switzerland took part in the Ares IV mission. (VOY: "One Small Step")
The Swiss flag could be seen on the Ares IV model amongst others.
In 2143, the Ariane 1 assignment patch, which was on display in the 602 Club, bore the flag of ESA member Switzerland. (ENT: "First Flight")
In the 2370s, while planning a date, Tom Paris asked B'Elanna Torres if she would like skiing in Saint Moritz, Switzerland. (VOY: "Waking Moments")
According to the Star Trek Fact Files, Switzerland would go on to become a member of the International Space Agency in the early 21st century.
In the final draft script for the Star Trek: The Next Generation first season episode "Angel One", Wesley Crusher and two buddies of him went to a skiing trip to the Swiss Alps on the holodeck instead of the Denubian Alps.
In a scene cut from the third season episode "Evolution", Annette and Eric, two of Wesley Crusher's friends went skiing on the holodeck in Switzerland.