I live in NW Iowa and while pheasants were du jour in Iowa in decades past, I can only say that while there are still birds, and some good areas comparatively, I wouldn’t be inclined to recommend Iowa for a long, cross-country trip.
Our group travels a bit further west to SD if that tells you anything, and we do it mid-December when the out-of-state rush is mostly over. It can be mild and beautiful but we’ve hit winter snow storms and -20* wind chills too — it’s the western Midwest after all. And there are designated walk-in areas where you can find birds though you will work for them; you can find these areas mapped on SD’s fish & game website. In regard to this time of year, I would strongly recommend you plan on camping in a motel if considering SD Late in the year..
I can’t comment on Kansas or Oklahoma.
