Your belief is that gender is a social construct and sex is biologically determined. “Gender is a social construct” is your belief. Many people in America do not share that belief. Many other people believe gender and sex are interchangeable concepts.

I’m trying to avoid picking a side here. It’s a tough one because I think whichever side you correct, it sounds like you’re taking the opposing. I would just as readily say if you believed gender and sex are interchangeable concepts that that is only your belief and you should remain open to the ideas of others believing gender is a social construct distinct from sex.

The key is to acknowledge truth and correctness and how things are is subject to your belief system. In this case, distinction between gender and sex is a relatively new concept (~50 years) and gaining ground in public opinion. We tend to say how things are based on majority belief and in this case your belief is near or perhaps already exceeded majority. I expect your belief is going to be on the right side of history but today it’s important to see the division.