I think you are having trouble OP because it really is a complex topic.
One major reason is because sex is a material reality which has material consequences in the world. For example, the potential for pregnancy, or differernt athletic profile. This means women have material common interests that they may want or need to pursue together, like a sporting event.
And while there has been some attempt in recent decades to downplay how much our sex impacts us, and technology has made that seem like a real thing, I think the reality is that it's one of the really biggest elements of who we are, it affects our whole experience of relating to each other, our physicality, our emotions. It also has a huge impact on how our life is likely to be shaped.
Race, on the other hand is almost completely socially constructed. Ethnicity has some material element, but we define race according to what are in many ways arbitrary lines. People can be "mixed race" which in some ways is almost a meaningless category, different societies delineate races differently, and they were often divided differently in the past as well.
As an example - Where I come from, for example, if someone is black, it means they have at least one parent of African descent. Some who would be considered black there would be "mixed-race" in the UK. My partner, who comes from another country, would call anyone who is not of European descent black, including Asians, middle eastern people, and various sorts of Native American groups. None of these are wrong or incorrect because there is no scientific or empirical line that can be drawn around the definition, it's social convention.
So there is really little that people in these arbitrarily defined group have inherently in common. Where they do, it's usually for social-historical reasons in a particular place, for example in North America there could be an interest in the civil rights movement among people who would have been affected by historical laws affecting people with African ancestors.