Defining one's political identity once meant something. The polities of ancient Greece were all more or less independent from one another though, broadly, they shared the same culture. However, the economic and structural design of each polity led to variation in approaches to the sciences, to art and to philosophy, which basically means that each polity had its own culture within the greater cultural region of Greece.
This concept is somewhat lost on us since we've been living under the American empire. States are not polities, nor are towns and counties. Under a democratic regime, political identity is no longer about what you share in common with the people around you. Under a democratic regime, your political identity, by nature, is a statement of antagonism toward your neighbors. It perpetuates the war of all against all and calls it liberty and fraternity.
It would seem today that political identities are largely unavoidable, though people invest into them the same degree of unwavering faith that people tend to devote to exoteric religion. To Call yourself a Communist is not unlike the Vedic attitude to offer up all actions to the divine as a sacrifice, only with Communism, one turns all of one's actions, energies and thoughts toward that sustained idea of revolution. To be a far Rightist is to subordinate all practical matters to an ideal zeitgeist to occur within culture which will govern and reconfiger everything else. Every political identity can take on a religious significance.
The main problem with how we form political identities today is not unlike the problem with how we form religious identities. You'll hear lots of talk today, especially amongst those who are trying to be fair and even-handed in their overview of western politics, that people are being too 'tribal.' If anything, the reason we are failing and confused about our identities is because we aren't tribal enough. Our identities are too wrapped up in the punishment/reward system which the western empire has manufactured largely through subtle marketing tactics, schools which brainwash children and young adults, and an entertainment culture which reflects back onto us images of people who make us feel good about our low standards for ourselves. Any tribes which result from the current system are inherently designed for us to culturally police each other, specifically with the intention of destroying the ones who pose the biggest danger to the state. Imposed identities are prisons. This, I believe, is why you see such a proliferation of identity politics, both the Left SJW variety and the Right ethno-nationalist variety. The historical veracity of the claims either side make are ultimately irrelevant, as they are results of imposed state antagonism and not even threats to it. If anything, these identity politics help strengthen the role of the state as it must ever mediate between the abstractions of these ever stratifying political constituencies - mere statics which come in handy during election cycles.
After the Protestant Reformation, institutional Christianity fractured in such a way that we have yet to see the full implications of this event even today. Now, it is taken as a given that people in the west should be able to choose their religion or practice it in private. To exit Christianity once meant that one exited the economy itself, exited society, and even exited the sympathy and good will of anyone close to one. Today, it only upsets family members and friends who, at the very worst, can disown you, though they would be unable to keep you from starting a new life, a career, or even a new family.
On the other hand, we know what happens today when people try to exit the western empire. It is much like exiting the church six hundred years ago. The police smash your ballot boxes. The banks make your credit system vanish. Rebels riot around your government buildings and foreign embassies. You get shut down.
Ideology poisons everything. Politics today is invariably ideological. Religion only does damage when it enters the politicization of everyday life. We are still at a stage in our history when political ideas are vying for universal control of all the others and the subordination of every experience that is heterogeneous to the political domain. The more political life becomes, the more politicized identity becomes.
Identity exists in layers and fluctuates. There is no reason to suppose that someone with one set of political ideas should subordinate them to someone else's, unless they disrupt the localized maintenance of peace. Just as churches are organic expressions of people's values, so should communal models be expressions of people's values. This is already taking place as people form communities online which then become real life communities. However, they are currently being forced to exist in the margins between brash forms of what people are calling 'populism,' which is really just what happens when the spirit of democracy gets ahead of itself and reaches beyond the realm of institutional representation.
Identity only seems like such an ugly thing to us now because it quickly becomes codified and reinterpreted in order to be deployed, not only for the sake of market competition, but in order to lock everyone into positions by which they can be of some use.
Do not adhere to identities to be of use. Do not allow your position to become codified from above. Become valuable through the realization of goals, and find other like minded people. Cooperative models will outlast a self-destructing empire even as it falls around us.