Let's start with a false but convenient dichotomy. Let's make a distinction between societies and cultures.
A society is made up of many things, but for our purposes, let's say a society is a voluntary collection of a people or peoples, a language or languages, and a method or methods of ranking. I say "voluntary" because rebellion and dropping out are the means by which one society leads to another. People can volunteer to leave or join societies. Immigration and conversion are two well known routes of moving from one society to another.
Within a society, there has to be a certain amount of agreement, or rules, that define how the society will continue. There are also stakes to be had, which we call a society's values. Wealth, honour, distinction, praise, and celebrity are all common stakes that are being competed for within a society. The rules define the value of these stakes. One has to have found a means within the rules to the acquisition of stakes for those stakes to be of value. Adultery of this value by breaking the rules is an essential adhesion-force in societies, and if rules are disregarded enough, a society is said to no longer exist.
The process of colonialization occurrs when one society's rules inveigle another to the point where one society is able to parasitize the other. The parasite is called the colonial power, and the society under dissolution is called the colony. It is accomplished by replacing peoples, language, or rules/ranking with those of the parasite society. Because of the internal cohesion-force of societies, this situation almost never goes well for the parasitized culture, because conflicting directions of censure tend to force splits within the society. Conflicting loyalties and conflicting senses of justice war with each other. This war occurs in all aspects of a society, in the mind, in the family/social group, and in the economy/judical system/stakeholder's marketplace.
The "global society" or globalization, is the ultimate parasite in this case. It provides a set of international and intersocial rules which serve the most dominant stakeholders. From the perspective of globalization, all societies are fodder for parasitization.
By contrast, a culture is also a voluntary collection, but instead of people, it's made up of symbols, traditions, and a narrative or iconology that arises from the combination of symbol and tradition. The stakes being competed for within a culture are more subtle and difficult to define, but they boil down to "meaning", where the persistance of a cultural icon is dependent on the meaning it provides and the meaning that is re-inforced/re-inculcated through a placing of importance on the icon and the repetition of its narrative.
In this way, a culture doesn't have rules that enforce it, but may adopt rules and rule-systems into itself in order to acheive meaningful narrative/iconology. In this way, cultures which exist within provincial or isolated societies become very integrated into the societies in which they arose, and it may be hard to distiguish, in many cases, where a social cohesion is being replaced with a narrative. Biblical interpretation has become a bugbear of European culture and its colonial offshoots, for example, and the shifting cultural underpinnings of religion frequently come into conflict with social authority.
Another social intrusion into culture is the "definitive narrative". This occurs when the rules of a society attempt to enforce a single narrative from a culture and attempt to enforce it in any other stakeholder arrangement. Copyright and academic tradition fall into this category of social-cultural interaction. Culture is "dead" when it can no longer adapt or generate new narrative, so this is a social triumph over culture which may occur on any scale.
But cultures are also social bridges. They provide a no-social-stakes arena through which individuals and groups of one society can participate in the society of another group. The cultural meaning that arises from these meeting-places often becomes a dynamic force in both socities, since it provides new narratives and new means by which conflicts between social cohesion-forces can be adapted and circumvented.
But except in extremely isolated situations, which are very rare in our current state of exploration and communications technology, there is no clear boundary between one culture and another. Cultural influences can be said to have greater or lesser meaning closer to certain centers and away from certain margins, but in any living culture, real barriers between one culture and another are not definable.
So, ultimately, there is one culture. Anyone from any society can participate, and the stakes are only to achieve as much meaning as possible.