There are about two hundred nations, or de facto sovereign states, in the world, of which, most are internationally recognized as separate nations, whereas others such as Taiwan, with a population of just over 23 million peoples is considered by China to be "an inalienable part of China" and therefore a province of China, though twenty-two nations recognize Taiwan (Republic of China) as the legitimate government of China, instead. Then there is the Turkish Republic of Northern Cyprus (TRNC) which is a self-declared state recognized only by Turkey.
The creation of new countries and the recognition of such is complicated, often involving bloody and long civil wars, in which the divisions that create the desire for a new nation state, are based typically on differences in regards to religion and/or ethnic identification, in which the opposing sides are not able to successfully come to a state of accommodation with one another, for a lot of reasons, which often involve justice and legislative laws having being constructed in a manner in which one group, is strongly favored over another, so much so, that the minority or the group that is out of power, has little or no say within their country, so that they are at best, treated as second class citizens, and at worse, purposely hunted down and killed by military forces or paramilitary forces and/or forcefully displaced in a trail of tears.
So too, the separation of peoples so as to create a new independent country, can work out to benefit of both nations, as for instance, the United States and Great Britain, which is no doubt, the best example of such, whereas the division into different nations, such as North and South Korea, in which the peoples of each nation are essentially ethnologically the same, are separated fundamentally by ideological differences. Then, there are peoples within nations that are without a country, such as the Palestinians in the Middle East, of which, after the creation of the state of Israel, in which essentially the Palestinians were displaced, they have not been able to create their own nation state, so that having no state, they have no democratic vote, and hence no real power of self determination.
It is important to recognize, first and foremost, that people that clearly identify with a specific religion, or a specific ethnicity, that live within a country that provides them with little or no power of voice or vote, have effectively been denied a basic human right, which is liberty. This then leads to the rather reasonable call, especially when the situation is one of long standing, and appears to be intractable, that these people should and deserve to be free from the constraints that keep them in bondage to the country that they reside in, so that, there should be, a viable forum, that adjudicates these matters in a fair and equitable way, and in situations in which certain countries have a direct and vested interest in the outcome, those countries should recuse themselves from such decision making, rather than being a barrier to progress and fairness.
Every person wants to feel that their homeland really is their homeland, because for those that do not have a country, they are effectively categorized as to be the orphans and bastards of humanity.