By the time of TNG, GR seemed to have become more of a globalist or thought that globalism would be the real Utopian future. The first episodes of TNG show the crew being oblivious at the idea of former nations and thought those beliefs were primitive. In fact, they are so ashamed of that that not even schools teach children what are flags and what they mean. I get that Worf, Tasha or Troi didn't know any of that, but there is no way Riker or Geordi didn't if they ever read any book written by a human author.
Only Picard seemed to know about past history, but it was treated like a rare trivia fact: "pfff, there was a time when humans have countries and flags...". Yeah, a time of almost all of modern human history.
Even non-college educated adults of today know that Earth was once divided by past empires, even if only some basic knowledge. These people who have easy access to all the knowledge of Earth and are basically their ambassadors in Space, don't. I guess that planets are the new nations, but it still made the Enterprise crew look like either arrogant people or simply uneducated imbeciles.