[2019] Is this a bug or did they add super nukes?

Thanks for the report! After looking into this, it sounds like a visual issue that can happen when you join an Adventure mode world after playing Nuclear Winter. So, the actual nuke zone is still normal size, it just looks huge on the map! If you log out and return to Adventure mode nuke zones should appear normal on the map again.

We're looking into a fix for this with a future update.

Glad to hear that! I'll pass along the kind words, thank you. :)