There have been gender neutral bathrooms in multiple US states for years now. Find me one single example of what you're describing occurring. This fear you have is founded in nothing but ignorance, xenophobia, and stupidity. It's literally the point of this post. You're no different than the white women in the 50s worrying about black people getting access to their bathrooms and victimizing them somehow.
Then you wait until you get home or to an otherwise appropriate venue. No one wants to hear a tutorial they didn't ask for about putting up drywall on their commute home or in the grocery store.