Still, I don't think we can face planetary-scale challenges much longer as a bunch of competing nations; some form of global governance will be necessary for humanity to move forward.
As for culture difference, this may be unpopular opinion, but I do hope things will homogenize further over time. The driving aspect towards cultural unification even today is that people copy what works.
https://en.wikipedia.org/wiki/Socialism_(disambiguation) https://en.wikipedia.org/wiki/Social_democracy
Yeah a "Great Leap Forward" kind of moving forward for humanity? Sounds good, works bad. Capitalism looks bad, but works good. I once also wanted a kind of world government but as I grew more knowledgable this Idea really started to terrify me. A decentralized world of competing small units with a small set of (trade) rules seems like the best option mid- to long-term. In short term of course socialist type of governance gives stability. Just 2 cents from a fellow European
And if you’re an American, the prospect of that single national government being say Bangladesh (https://www.nytimes.com/2017/05/26/world/asia/bangladesh-sta...) should be pretty scary! Star Trek style global government seems attractive to many people because they assume it’ll be “America in Space.”