The vastly complex system of interdependencies linked to globalisation could be the some early stage of that. Ironically this theatre is also where those made-up problems of ours can very quickly turn into real ones.

Being part of only a single group isn't really our thing though. Without something external to focus on we quickly tend go down this path of surprisingly efficient self-destructive behaviour that often involves lots of heavy weaponry. We are chaos incarnate :)

Perhaps, but the groups have subgroups and those have subgroups and so on until the individual. The world as a whole may get more integrated, and the exact way that dividing lines between the groups work may change (e.g. not so focused on geographic areas and more mutable), but I think it will always be there to some extent.

Can't have an us without a them