First of all, to reiterate, trans women are women. The word for women who are not trans is not simply "women", it's "cisgender" or "cis" women.

Regarding the comfort level of cis women, some of them are uncomfortable with Black women sharing their restrooms. That doesn't mean we keep Black women out of restrooms, or make sure that no non-Black women are using the restroom before they go in. There is no difference here. It's bigotry and ignorance, pure and simple.