You didn't say if you are now a Swiss citizen or are still a US citizen.
I bring this up because it's fairly easy to find info on FOREIGN NATIONALS driving in the US. Basically, they can drive in the US with their foreign license, but some states require you to also have an International Driving Permit (IDP) which is a standard form on which the info on your driver's license is translated into several common languages - English, French, Spanish, Arabic, etc.
Whether that would apply to a US citizen resident in another country, I don't know. Perhaps a US Consulate in Switzerland could clear that up for you.
There may be one other problem, too. I've heard that some foreign driving licenses will state a limit on how HEAVY a vehicle you can drive - it Gross Vehicle Weight. If your DL lists such a limit, and the motor home you want to drive exceeds that, that may be an issue.
https://www.usa.gov/visitors-driving