Is it? Pretty sure when you come out of your mother's vagina they check your genitals and you are properly assigned. Gender has always been based and rooted in biology. There is a difference between "norms" and "constructs".
A
social norm is an expectation that a person will do something because everyone else does it, or often does it. These norms can vary based on family, friend group, work environment, country, continent, etc. For example, among one group it might be a social norm that families always eat dinner together every day, while other people might emphasize the breakfast meal. In some societies, young people are expected to go to college (post-secondary education), while in other places they may not be expected to. In some cultures, the word of an elder is highly respected and their authority may not be challenged, while in other cultures younger people speak their minds without restraint.
A
social construct is a way of looking at the world that is not defined by the laws of nature or physics but by mutual agreement among people in a society. For example: time exists everywhere, and people on earth experience the passage of time in the same way, but
time zones are a social construct. There is little inherent value in pieces of paper, but we say that
paper money has great worth; that is a social construct. A person's
external genitalia are objective and physical, and a person's
sex is related to their chromosomes and external genitalia, but
gender is a social construct that is rooted in sex/biology.
Social constructs are important. When a 5-year-old points at the sky, a tree, a person, or even their own genitalia they are trying to make sense of the world. Constructs are designed to make sense of the world. That penis signifies something in our social world. When kids start pointing at things and society starts saying that penis can mean anything you want it can get confusing at the very least.
Using my Christian values. Men have roles in child rearing and other things as do women. Those roles are clearly defined in the Bible. In my "narrow-minded" Christian value system a dick means you are a man, the vagina means you are a woman. God/Jesus clearly defines this for me. The moment I deviate from God's plan and design I am deviating from God/Jesus. When I die and I stand before Christ I highly doubt he will take into consideration that societal norms trumped his will and design.
The biblical understanding of male and female is more than just an assumption written large on the pages of Scripture. We know from
Genesis 1 and 2 that the categories of male and female are a part of God’s design for humanity. Indeed, when God created the first human pair in his image, he created them male and female (
Gen. 1:27). He made the woman to be a complement and help to the man (
Gen. 2:18-22). Far from being a mere cultural construct, God depicts the existence of a man and a woman as essential to his creational plan. The two are neither identical nor interchangeable. But when the woman, who was taken out of man, joins again with the man in sexual union, the two become one flesh (
Gen. 1:23-24). Dividing the human race into two genders, male and female, one or the other, not both, and not one then the other. It is not the invention of Victorian prudes or patriarchal oafs. It was God’s idea.
If the Bible is inconvenient for you try Islam or atheism or even the occult. They are always recruiting and looking for members and you would already have a leg up in disagreeing with Jesus and his teachings.
But I will repeat. We live in America not Heaven. Laws in this fallen world do not have to align with God's word. God gave us this gift of free will and commanding all the people of Earth to fall in line would be stealing someone's ability to exhibit their free will. Do as you will, I will do as I will.