Can I delete a warehouse?

No, once the stores are created they cannot be deleted, but you can access the store and click on the "hidden" tab so that it is not displayed.

From the users account if this store is hidden it will not appear within the Multistore > My stores section, neither will they be able to view this store from Catalog > Products > Warehouse filter (where only the warehouses over which they have visibility/realization permissions will appear).

Catalog > Products > Warehouse filter.

To re-enable it you must do it from the super admin user, accessing Multistore > My Stores > click on the store > Edit > uncheck Hidden.