I guess there can be a good proposal for an international government in which there are no independent states but the question comes who will rule it? Certainly, Africans would never accept any international system in which Europeans would be the ruling elite and they would be living in slavery. Similarly, there may be a conflict between religions and culture etc.
as with the comment below I don't think a singular centralised government could be good as extraterrestrial rule :D I think it's up to us and it's not that hard if we stop playing against each other just exchanging blows in stupid games called finance and law, it would be harder but imagine people working towards reason and responsibility rather than playground politics ...
I don’t think an international government would be very positive as it is more likely to benefit some more than others, more like a coalition of communities that are willing to stay out of each other’s business but also help and support each other when needed.....Something like the UN but less influences by the interests of nations and more focused on the interests of regular people. We can still have borders and nationality but our humanity can extend beyond them as we do not need our country to be #1, we want all of humanity to rise together.
I don’t suggest a formation of a new organization anytime soon though. As we change our perspective and resources spread, we can focus on our own communities first and build something from the bottom up, then the organizations that can adapt will, the others will shed away naturally.