Gender marker change + passports

Can someone explain me what is happening in USA right now? There are not good informations about it. Trans people right now get new passports with birth sex even when they changed every documents to correct gender. So it means that right now you can't change your gender marker on every documents? And you will get new documents back to your birth sex? I'm not from USA but if I want to travel there with my changed gender marker on my passport they will know that it was changed and I would be reject? How is that even possible and how can they know? It's really scary and I don't get it.