As I mentioned earlier, I believe the world would be much better off with people primarily identifying themselves as part of the human family. As my example of Iraq indicates, people will tend to identify with smaller groups anyway, based on factors directly applicable to their day-to-day lives such as health and wealth.
The point I’d like to make here is that we can, and should, have competition over strategies and methods rather than goals. Goals are associated with our identity, while strategies and methods are associated with our experience, capabilities, resources, and intelligence. Historically, strategies and methods have been enshrined in our culture, thereby being conflated with our identity. To survive as a world community, either our identities need to be disentangled from our cultures, or our cultures must be melded together, ideally based on shared goals.
The second option is already being tried, but without people necessarily agreeing on shared goals. Competing cultures have used economic and military approaches to achieve dominance, with mixed results. Neoconservative imperialism and radical Muslim attempts to create a worldwide caliphate are two of the latest examples of this, coming close on the heels of the Cold War struggle between democracy and communism.
As I’ve implied, the problem with melding cultures is that people must have shared goals for it to ultimately succeed; and for this to happen, people have to choose their goals (and their identities) voluntarily. This problem is being partially addressed by the United Nations, which provides a forum for establishing a common set of goals, and, through communication, a stronger sense of community among its members. The attempts at unification have been hampered by nations such as the United States (at least recently) that want a rubber stamp on their own particular set of goals, assuming they naturally speak for everyone, and justification to squash those that (in their minds, foolishly) disagree with them. Iraq is a perfect example of what happens when a set of goals is rammed down people’s throats: They rebel, as anyone would.