Earth in the Star Trek Universe

I still have the theme of the 2008 Summer Games in my head: "One World, One Dream" and I have been watching my Star Trek Deep Space 9 series again from the beginning. I got to thinking about earth in the Star Trek universe and how it is unified. There is a central government, poverty has been erased, everyone has shelter, there is no need for money. Humans simply work and produce to better themselves. The other worlds in this same universe, such as Bajor, Vulcan, Cardassia, also have a central government, one language, and a common philosophy of life. Of course there are still conflicts, but they are seen as challenges to overcome, wrongs to be made right.
I love this vision in Star Trek, that one day humans can evolve to the point of cooperation and live together in peace. That hope and positive message is what keeps me returning to the series and watching and reading.
This brings me back to the recent Olympics and how for a few weeks in a concentrated area in China, people from all over the world came together in friendly athletic competition. Almost everyone got along and enjoyed meeting each other ( I assume).
My question is: Can we overcome the human condition and work together as one? Our cultures are so different and the first barrier would be language. How can we communicate with each other to understand better one another? Can people become selfless and trust a central government that would exist simply to keep Earth and its inhabitants fed and sheltered? So far, our history is filled from past to present day with battles about boundaries, discrimination, and struggles for power. Will it ever be possible to move in the direction of the peace and acceptance we find in the Star Trek Universe? I sincerely hope so.