A Community is a group of people sharing a particular characteristic, or certain attitudes/interests. Community is a trust tool that immediately establishes rules of engagement with someone you don't know, or allows you to build a life with people you know deeply. In the clash between global and local, this is a difficult challenge. How do you create trust, in a global world with lots of different local conventions? The 'global community' has to, by definition, be quite superficial. It has to accommodate very different communities.
Defining a community by particular characteristic is an arbitrary rule, but it is useful as a signal that is harder to fake. The underlying attitudes/interests are the more important thing.
I am deeply uncomfortable with my community being based on people I share attitudes/interests with. I grew up in Apartheid South Africa, where the lives of people on different sides of a road can be vastly different. The idea of self-determination where a community takes on the role of self used those 'arbitrary rules' in order to embed trust. This allows communities to extend their 'circle of care' beyond themselves, but selectively, and destructively.
The world has 7.5 Billion people. We can't know those people. We can't build the kinds of relationships you need to trust people when there isn't thousands of years of deeply wired understanding to help. If the world were 100 people, we could put names and faces to those people, and start. Still, would there be enough common ground to develop deep relationships? Only 5 would be English speaking. Three English guys would mean they were over-represented. Add age as a filter and no one can be 'like me' on just three criteria.
Somewhere between the wide of Global and the deep of Local lie some beautiful questions.