I ski the Divide in Colorado weekly. Snow conditions on the Divide itself are usually pretty terrible because of the wind, mostly blown clear above treeline. Cycling up there would be possible in spots on good weather days, and there are two or three of those every month.

There's deep powder deposition on the lee (east) side, often with extreme avalanche danger. Skiing in that powder, I'm often up to my knees or deeper, meaning the pedals on a bike would be foundering in it. I see plenty of fat bike tracks on popular trails already packed by snowshoers and snowmachines, but they don't go far off into the untracked powder.

Part of southern New Mexico would be possible, and maybe across the Red Desert in Wyoming, again given decent weather when the wind drops below 40 knots or so.