- I can't figure out where to pick up the quest "A Nation United"
- I don't have the quest "A Nation United"
If the quest A Nation United isn't available, you may not have met the requirements to get the quest. In order to obtain the quest, you must have completed the achievement Loremaster of Kul Tiras, completed the quest line Pride of Kul Tiras and any follow up quest.
To learn more about how to obtain the quest, you may want to consult third-party sites like WoWHead, WoWDB, or Icy Veins.