Can I sell a mobile home that is affixed and keep the land

You easily can if the mobile home has a title like a car and the land has a separate deed. You can then sell the home and "rent" the land to the new homeowner. I've seen this scenerio done many times.

When you say the mobile home is "attached" what do you mean.

Is the moble home build on, with a room or two added,

But if you merely mean it is sitting on the land, maybe with tie down straps and underpinning, it can be sold, as long as it is not included in the mortgage for the land.