But even if we would have frontiers for expansion (the window of opportunity opened once more thanks to Rosetta) we are stuck with a suffering environment, not to mention human suffering.
You'd have to ignore the plight of the Native Americans, for whom the suffering still isn't over but also take into account that as soon as that Western Frontier was closed, the suffering of the rest of the world began (see America's expansion-politics which date in more covert forms back from the early 1800's).
Yes, art, culture, laws have benefited, for a time. But the complexity with which laws for example have formed have nothing to do with justice anymore, only with legality. And right now that means that whoever has the big bucks makes the rules. And the rules are kept in place to profit, which inevitably means there has to be suffering (for without it, many flourishing businesses would cease to exist. THat will vex the companies' respective shareholders).
Art, music, transport, communication: it's no longer about improving the all-over state of the species (which one could state when talking about the old inventions) but to make a fast buck and plenty of them. The idea of programmed obsolescence abhors me to the core. In other words, what is there to expand TO? We haven't even been able to fix our already existing problems, how would we ever be able to get it right if we were to explore/colonise/utilise other comets or planets? You cannot fix problems using the same attitude and tools which have created the problem in the first place.
I'd argue that political and cultural change most often follow technological change. Personally, I think we are on the verge of another technologically-driven upheaval, and that space exploration will only play a very small role, if any. I believe that our cultural systems are a reflection of social systems that are technologically possible and stable. Our situation will not be undone by political will, but by new technologies that make it obsolete. What we learn from space exploration can be a component, and I think it would be a positive one; I don't think all of them are.
In a word: decentralization. I believe that we are entering a new phase where the systems of nation-states are going to increasingly run counter to the realities of human interaction. In short, our technologies are going to enable global organization and exchange between people that will require new political structures. Probably something more fluid than any republic can offer. cc thundara