Might be sample bias, but I know three people which successfully did it, seen some obviously American cars with Swiss plates, and even read some stories of successful registrations on EF.
Import car from USA to Switzerland
And others.
This was a great post, thank you for posting it here, very helpful!
Seeing a little light at the end of the tunnel.
From what it seems like, the form that the DMV in Ticino sent to us, needs to be filled out because there is no Certificate of Conformity. So either a CoConformity or this form, which must be filled out by a manufacturer. Another poster talked about Form 18.44 (household goods imported), which he apparently got from the customs people and is in addition to Form 13.20, also a customs form.