A Singular Nation?
Matt Weiner of Opiniatrety wonders about sports team "nations": do they get the singular or the plural? Is it...
Steeler Nation or Steelers Nation?
Raiders Nation or Raider Nation?
Eagle Nation or Eagles Nation?
49ers Nation or 49er Nation?
Ram Nation or Rams Nation?
Patriots Nation or Patriot Nation?
Red Sox Nation or Red Sox Nation?
Form your own opinions, then go see his Google-informed opinion.
Have you gone and returned? Now, you can take a look at a few examples that I found where the plural has a clear advantage:
Jets Nation (352) over Jet Nation (29)
Browns Nation (116) over Brown Nation (19)
Chiefs Nation (32) over Chief Nation (6)
Note: I included the name of the city in the searches to minimize false positives. This only significantly reduced the number of hits for 'brown nation' and 'chief nation', and evidence suggests that the cases that were left out were almost all irrelevant.
It may not be a coincidence that the plural is more common when there are many unrelated hits for the singular form. To my ear, the singular sounds weird in all three cases due to the meaning of the team's name. You need to use the plural for it to sound like you're talking about the sports team.