maybe you need an american appleid, who knows?

According to Chatgpt:

Yes, Apple Intelligence is available in Switzerland. The first functions were introduced with the release of iOS 18.1, iPadOS 18.1 and macOS Sequoia 15.1 in October 2024. From April 2025, Apple will expand support to other languages and regions, including German in Switzerland.

Certain functions already work in the IOS 18 beta, including in Switzerland. However, most of them will not be added until 2025 and it is not yet clear whether all functions will be available in Switzerland.

If then only in English, if you adapt your system language accordingly.