..one of the pillars upon which the World Government theory is built is the Translight travel idea to colonize distant stars....We're stuck in this solar system..
Depends on how fast technology advances; it's logarithmic, so that may be possible by 2100 or so. In any event, the solar system alone should keep us busy a while.
And the raisen d'etre of a World government is also to establish permanent stability, and solve other earthly problems, notably environmental ones.
..how do you plan to build a Terran Identity and de-emphasize national ones?
This has been underway already for some time with rapidly enhanced means of communication, immigration, and miscegenation. Also, again, look at the US, where people of every existing race and nationality blend together as Americans. The US of A could become the US of the world--minus democratic/religious bs of course. But there may be another key factor. Even if aliens don't exist, global authorities will have to invent them.
But honestly, I don't think that'll be necessary, given, for starters, rapid progress in exoplanet hunting.
Nationalities will be maintained parallel to the Terran identity.
I think nationalism or old ethnic identification will fade alongside it. Even the Roman Empire was able to assimilate all kinds of people, and give them a whole new identity.
Andropov's version of fascism is very underdeveloped and is a bag of contradictions of the worst sort.
I've pointed out inconsistencies, but we should appreciate and welcome anyone with the right basic orientation.